Git support for package fetching.
This is not intended to support all features of Git: it is limited to the basic functionality needed to clone a repository for the purpose of fetching a package.
//! Git support for package fetching.
//!
//! This is not intended to support all features of Git: it is limited to the
//! basic functionality needed to clone a repository for the purpose of fetching
//! a package.
const std = @import("std");
const Io = std.Io;
const mem = std.mem;
const testing = std.testing;
const Allocator = mem.Allocator;
const Sha1 = std.crypto.hash.Sha1;
const Sha256 = std.crypto.hash.sha2.Sha256;
const assert = std.debug.assert;
/// The ID of a Git object.
pub const Oid = union(Format) {
sha1: [Sha1.digest_length]u8,
sha256: [Sha256.digest_length]u8,
pub const max_formatted_length = len: {
var max: usize = 0;
for (std.enums.values(Format)) |f| {
max = @max(max, f.formattedLength());
}
break :len max;
};
pub const Format = enum {
sha1,
sha256,
pub fn byteLength(f: Format) usize {
return switch (f) {
.sha1 => Sha1.digest_length,
.sha256 => Sha256.digest_length,
};
}
pub fn formattedLength(f: Format) usize {
return 2 * f.byteLength();
}
};
const Hasher = union(Format) {
sha1: Sha1,
sha256: Sha256,
fn init(oid_format: Format) Hasher {
return switch (oid_format) {
.sha1 => .{ .sha1 = Sha1.init(.{}) },
.sha256 => .{ .sha256 = Sha256.init(.{}) },
};
}
// Must be public for use from HashedReader and HashedWriter.
pub fn update(hasher: *Hasher, b: []const u8) void {
switch (hasher.*) {
inline else => |*inner| inner.update(b),
}
}
fn finalResult(hasher: *Hasher) Oid {
return switch (hasher.*) {
inline else => |*inner, tag| @unionInit(Oid, @tagName(tag), inner.finalResult()),
};
}
};
const Hashing = union(Format) {
sha1: Io.Writer.Hashing(Sha1),
sha256: Io.Writer.Hashing(Sha256),
fn init(oid_format: Format, buffer: []u8) Hashing {
return switch (oid_format) {
.sha1 => .{ .sha1 = .init(buffer) },
.sha256 => .{ .sha256 = .init(buffer) },
};
}
fn writer(h: *@This()) *Io.Writer {
return switch (h.*) {
inline else => |*inner| &inner.writer,
};
}
fn final(h: *@This()) Oid {
switch (h.*) {
inline else => |*inner, tag| {
inner.writer.flush() catch unreachable; // hashers cannot fail
return @unionInit(Oid, @tagName(tag), inner.hasher.finalResult());
},
}
}
};
pub fn fromBytes(oid_format: Format, bytes: []const u8) Oid {
assert(bytes.len == oid_format.byteLength());
return switch (oid_format) {
inline else => |tag| @unionInit(Oid, @tagName(tag), bytes[0..comptime tag.byteLength()].*),
};
}
pub fn readBytes(oid_format: Format, reader: *Io.Reader) !Oid {
return switch (oid_format) {
inline else => |tag| @unionInit(Oid, @tagName(tag), (try reader.takeArray(tag.byteLength())).*),
};
}
pub fn parse(oid_format: Format, s: []const u8) error{InvalidOid}!Oid {
switch (oid_format) {
inline else => |tag| {
if (s.len != tag.formattedLength()) return error.InvalidOid;
var bytes: [tag.byteLength()]u8 = undefined;
for (&bytes, 0..) |*b, i| {
b.* = std.fmt.parseUnsigned(u8, s[2 * i ..][0..2], 16) catch return error.InvalidOid;
}
return @unionInit(Oid, @tagName(tag), bytes);
},
}
}
test parse {
try testing.expectEqualSlices(
u8,
&.{ 0xCE, 0x91, 0x9C, 0xCF, 0x45, 0x95, 0x18, 0x56, 0xA7, 0x62, 0xFF, 0xDB, 0x8E, 0xF8, 0x50, 0x30, 0x1C, 0xD8, 0xC5, 0x88 },
&(try parse(.sha1, "ce919ccf45951856a762ffdb8ef850301cd8c588")).sha1,
);
try testing.expectError(error.InvalidOid, parse(.sha256, "ce919ccf45951856a762ffdb8ef850301cd8c588"));
try testing.expectError(error.InvalidOid, parse(.sha1, "7f444a92bd4572ee4a28b2c63059924a9ca1829138553ef3e7c41ee159afae7a"));
try testing.expectEqualSlices(
u8,
&.{ 0x7F, 0x44, 0x4A, 0x92, 0xBD, 0x45, 0x72, 0xEE, 0x4A, 0x28, 0xB2, 0xC6, 0x30, 0x59, 0x92, 0x4A, 0x9C, 0xA1, 0x82, 0x91, 0x38, 0x55, 0x3E, 0xF3, 0xE7, 0xC4, 0x1E, 0xE1, 0x59, 0xAF, 0xAE, 0x7A },
&(try parse(.sha256, "7f444a92bd4572ee4a28b2c63059924a9ca1829138553ef3e7c41ee159afae7a")).sha256,
);
try testing.expectError(error.InvalidOid, parse(.sha1, "ce919ccf"));
try testing.expectError(error.InvalidOid, parse(.sha256, "ce919ccf"));
try testing.expectError(error.InvalidOid, parse(.sha1, "master"));
try testing.expectError(error.InvalidOid, parse(.sha256, "master"));
try testing.expectError(error.InvalidOid, parse(.sha1, "HEAD"));
try testing.expectError(error.InvalidOid, parse(.sha256, "HEAD"));
}
pub fn parseAny(s: []const u8) error{InvalidOid}!Oid {
return for (std.enums.values(Format)) |f| {
if (s.len == f.formattedLength()) break parse(f, s);
} else error.InvalidOid;
}
pub fn format(oid: Oid, writer: *Io.Writer) Io.Writer.Error!void {
try writer.print("{x}", .{oid.slice()});
}
pub fn slice(oid: *const Oid) []const u8 {
return switch (oid.*) {
inline else => |*bytes| bytes,
};
}
};
pub const Diagnostics = struct {
allocator: Allocator,
errors: std.ArrayList(Error) = .empty,
pub const Error = union(enum) {
unable_to_create_sym_link: struct {
code: anyerror,
file_name: []const u8,
link_name: []const u8,
},
unable_to_create_file: struct {
code: anyerror,
file_name: []const u8,
},
};
pub fn deinit(d: *Diagnostics) void {
for (d.errors.items) |item| {
switch (item) {
.unable_to_create_sym_link => |info| {
d.allocator.free(info.file_name);
d.allocator.free(info.link_name);
},
.unable_to_create_file => |info| {
d.allocator.free(info.file_name);
},
}
}
d.errors.deinit(d.allocator);
d.* = undefined;
}
};
pub const Repository = struct {
odb: Odb,
pub fn init(
repo: *Repository,
allocator: Allocator,
format: Oid.Format,
pack_file: *Io.File.Reader,
index_file: *Io.File.Reader,
) !void {
repo.* = .{ .odb = undefined };
try repo.odb.init(allocator, format, pack_file, index_file);
}
pub fn deinit(repository: *Repository) void {
repository.odb.deinit();
repository.* = undefined;
}
/// Checks out the repository at `commit_oid` to `worktree`.
pub fn checkout(
repository: *Repository,
io: Io,
worktree: Io.Dir,
commit_oid: Oid,
diagnostics: *Diagnostics,
) !void {
try repository.odb.seekOid(commit_oid);
const tree_oid = tree_oid: {
const commit_object = try repository.odb.readObject();
if (commit_object.type != .commit) return error.NotACommit;
break :tree_oid try getCommitTree(repository.odb.format, commit_object.data);
};
try repository.checkoutTree(io, worktree, tree_oid, "", diagnostics);
}
/// Checks out the tree at `tree_oid` to `worktree`.
fn checkoutTree(
repository: *Repository,
io: Io,
dir: Io.Dir,
tree_oid: Oid,
current_path: []const u8,
diagnostics: *Diagnostics,
) !void {
try repository.odb.seekOid(tree_oid);
const tree_object = try repository.odb.readObject();
if (tree_object.type != .tree) return error.NotATree;
// The tree object may be evicted from the object cache while we're
// iterating over it, so we can make a defensive copy here to make sure
// it remains valid until we're done with it
const tree_data = try repository.odb.allocator.dupe(u8, tree_object.data);
defer repository.odb.allocator.free(tree_data);
var tree_iter: TreeIterator = .{
.format = repository.odb.format,
.data = tree_data,
.pos = 0,
};
while (try tree_iter.next()) |entry| {
switch (entry.type) {
.directory => {
try dir.createDir(io, entry.name, .default_dir);
var subdir = try dir.openDir(io, entry.name, .{});
defer subdir.close(io);
const sub_path = try std.fs.path.join(repository.odb.allocator, &.{ current_path, entry.name });
defer repository.odb.allocator.free(sub_path);
try repository.checkoutTree(io, subdir, entry.oid, sub_path, diagnostics);
},
.file => {
try repository.odb.seekOid(entry.oid);
const file_object = try repository.odb.readObject();
if (file_object.type != .blob) return error.InvalidFile;
var file = dir.createFile(io, entry.name, .{ .exclusive = true }) catch |e| {
const file_name = try std.fs.path.join(diagnostics.allocator, &.{ current_path, entry.name });
errdefer diagnostics.allocator.free(file_name);
try diagnostics.errors.append(diagnostics.allocator, .{ .unable_to_create_file = .{
.code = e,
.file_name = file_name,
} });
continue;
};
defer file.close(io);
try file.writePositionalAll(io, file_object.data, 0);
},
.symlink => {
try repository.odb.seekOid(entry.oid);
const symlink_object = try repository.odb.readObject();
if (symlink_object.type != .blob) return error.InvalidFile;
const link_name = symlink_object.data;
dir.symLink(io, link_name, entry.name, .{}) catch |e| {
const file_name = try std.fs.path.join(diagnostics.allocator, &.{ current_path, entry.name });
errdefer diagnostics.allocator.free(file_name);
const link_name_dup = try diagnostics.allocator.dupe(u8, link_name);
errdefer diagnostics.allocator.free(link_name_dup);
try diagnostics.errors.append(diagnostics.allocator, .{ .unable_to_create_sym_link = .{
.code = e,
.file_name = file_name,
.link_name = link_name_dup,
} });
};
},
.gitlink => {
// Consistent with git archive behavior, create the directory but
// do nothing else
try dir.createDir(io, entry.name, .default_dir);
},
}
}
}
/// Returns the ID of the tree associated with the given commit (provided as
/// raw object data).
fn getCommitTree(format: Oid.Format, commit_data: []const u8) !Oid {
if (!mem.startsWith(u8, commit_data, "tree ") or
commit_data.len < "tree ".len + format.formattedLength() + "\n".len or
commit_data["tree ".len + format.formattedLength()] != '\n')
{
return error.InvalidCommit;
}
return try .parse(format, commit_data["tree ".len..][0..format.formattedLength()]);
}
const TreeIterator = struct {
format: Oid.Format,
data: []const u8,
pos: usize,
const Entry = struct {
type: Type,
executable: bool,
name: [:0]const u8,
oid: Oid,
const Type = enum(u4) {
directory = 0o4,
file = 0o10,
symlink = 0o12,
gitlink = 0o16,
};
};
fn next(iterator: *TreeIterator) !?Entry {
if (iterator.pos == iterator.data.len) return null;
const mode_end = mem.indexOfScalarPos(u8, iterator.data, iterator.pos, ' ') orelse return error.InvalidTree;
const mode: packed struct {
permission: u9,
unused: u3,
type: u4,
} = @bitCast(std.fmt.parseUnsigned(u16, iterator.data[iterator.pos..mode_end], 8) catch return error.InvalidTree);
const @"type" = std.enums.fromInt(Entry.Type, mode.type) orelse return error.InvalidTree;
const executable = switch (mode.permission) {
0 => if (@"type" == .file) return error.InvalidTree else false,
0o644 => if (@"type" != .file) return error.InvalidTree else false,
0o755 => if (@"type" != .file) return error.InvalidTree else true,
else => return error.InvalidTree,
};
iterator.pos = mode_end + 1;
const name_end = mem.indexOfScalarPos(u8, iterator.data, iterator.pos, 0) orelse return error.InvalidTree;
const name = iterator.data[iterator.pos..name_end :0];
iterator.pos = name_end + 1;
const oid_length = iterator.format.byteLength();
if (iterator.pos + oid_length > iterator.data.len) return error.InvalidTree;
const oid: Oid = .fromBytes(iterator.format, iterator.data[iterator.pos..][0..oid_length]);
iterator.pos += oid_length;
return .{ .type = @"type", .executable = executable, .name = name, .oid = oid };
}
};
};
/// A Git object database backed by a packfile. A packfile index is also used
/// for efficient access to objects in the packfile.
///
/// The format of the packfile and its associated index are documented in
/// [pack-format](https://git-scm.com/docs/pack-format).
const Odb = struct {
format: Oid.Format,
pack_file: *Io.File.Reader,
index_header: IndexHeader,
index_file: *Io.File.Reader,
cache: ObjectCache = .{},
allocator: Allocator,
/// Initializes the database from open pack and index files.
fn init(
odb: *Odb,
allocator: Allocator,
format: Oid.Format,
pack_file: *Io.File.Reader,
index_file: *Io.File.Reader,
) !void {
try pack_file.seekTo(0);
try index_file.seekTo(0);
odb.* = .{
.format = format,
.pack_file = pack_file,
.index_header = undefined,
.index_file = index_file,
.allocator = allocator,
};
try odb.index_header.read(&index_file.interface);
}
fn deinit(odb: *Odb) void {
odb.cache.deinit(odb.allocator);
odb.* = undefined;
}
/// Reads the object at the current position in the database.
fn readObject(odb: *Odb) !Object {
var base_offset = odb.pack_file.logicalPos();
var base_header: EntryHeader = undefined;
var delta_offsets: std.ArrayList(u64) = .empty;
defer delta_offsets.deinit(odb.allocator);
const base_object = while (true) {
if (odb.cache.get(base_offset)) |base_object| break base_object;
base_header = try EntryHeader.read(odb.format, &odb.pack_file.interface);
switch (base_header) {
.ofs_delta => |ofs_delta| {
try delta_offsets.append(odb.allocator, base_offset);
base_offset = std.math.sub(u64, base_offset, ofs_delta.offset) catch return error.InvalidFormat;
try odb.pack_file.seekTo(base_offset);
},
.ref_delta => |ref_delta| {
try delta_offsets.append(odb.allocator, base_offset);
try odb.seekOid(ref_delta.base_object);
base_offset = odb.pack_file.logicalPos();
},
else => {
const base_data = try readObjectRaw(odb.allocator, &odb.pack_file.interface, base_header.uncompressedLength());
errdefer odb.allocator.free(base_data);
const base_object: Object = .{ .type = base_header.objectType(), .data = base_data };
try odb.cache.put(odb.allocator, base_offset, base_object);
break base_object;
},
}
};
const base_data = try resolveDeltaChain(
odb.allocator,
odb.format,
odb.pack_file,
base_object,
delta_offsets.items,
&odb.cache,
);
return .{ .type = base_object.type, .data = base_data };
}
/// Seeks to the beginning of the object with the given ID.
fn seekOid(odb: *Odb, oid: Oid) !void {
const oid_length = odb.format.byteLength();
const key = oid.slice()[0];
var start_index = if (key > 0) odb.index_header.fan_out_table[key - 1] else 0;
var end_index = odb.index_header.fan_out_table[key];
const found_index = while (start_index < end_index) {
const mid_index = start_index + (end_index - start_index) / 2;
try odb.index_file.seekTo(IndexHeader.size + mid_index * oid_length);
const mid_oid = try Oid.readBytes(odb.format, &odb.index_file.interface);
switch (mem.order(u8, mid_oid.slice(), oid.slice())) {
.lt => start_index = mid_index + 1,
.gt => end_index = mid_index,
.eq => break mid_index,
}
} else return error.ObjectNotFound;
const n_objects = odb.index_header.fan_out_table[255];
const offset_values_start = IndexHeader.size + n_objects * (oid_length + 4);
try odb.index_file.seekTo(offset_values_start + found_index * 4);
const l1_offset: packed struct { value: u31, big: bool } = @bitCast(try odb.index_file.interface.takeInt(u32, .big));
const pack_offset = pack_offset: {
if (l1_offset.big) {
const l2_offset_values_start = offset_values_start + n_objects * 4;
try odb.index_file.seekTo(l2_offset_values_start + l1_offset.value * 4);
break :pack_offset try odb.index_file.interface.takeInt(u64, .big);
} else {
break :pack_offset l1_offset.value;
}
};
try odb.pack_file.seekTo(pack_offset);
}
};
const Object = struct {
type: Type,
data: []const u8,
const Type = enum {
commit,
tree,
blob,
tag,
};
};
/// A cache for object data.
///
/// The purpose of this cache is to speed up resolution of deltas by caching the
/// results of resolving delta objects, while maintaining a maximum cache size
/// to avoid excessive memory usage. If the total size of the objects in the
/// cache exceeds the maximum, the cache will begin evicting the least recently
/// used objects: when resolving delta chains, the most recently used objects
/// will likely be more helpful as they will be further along in the chain
/// (skipping earlier reconstruction steps).
///
/// Object data stored in the cache is managed by the cache. It should not be
/// freed by the caller at any point after inserting it into the cache. Any
/// objects remaining in the cache will be freed when the cache itself is freed.
const ObjectCache = struct {
objects: std.AutoHashMapUnmanaged(u64, CacheEntry) = .empty,
lru_nodes: std.DoublyLinkedList = .{},
lru_nodes_len: usize = 0,
byte_size: usize = 0,
const max_byte_size = 128 * 1024 * 1024; // 128MiB
/// A list of offsets stored in the cache, with the most recently used
/// entries at the end.
const LruListNode = struct {
data: u64,
node: std.DoublyLinkedList.Node,
};
const CacheEntry = struct { object: Object, lru_node: *LruListNode };
fn deinit(cache: *ObjectCache, allocator: Allocator) void {
var object_iterator = cache.objects.iterator();
while (object_iterator.next()) |object| {
allocator.free(object.value_ptr.object.data);
allocator.destroy(object.value_ptr.lru_node);
}
cache.objects.deinit(allocator);
cache.* = undefined;
}
/// Gets an object from the cache, moving it to the most recently used
/// position if it is present.
fn get(cache: *ObjectCache, offset: u64) ?Object {
if (cache.objects.get(offset)) |entry| {
cache.lru_nodes.remove(&entry.lru_node.node);
cache.lru_nodes.append(&entry.lru_node.node);
return entry.object;
} else {
return null;
}
}
/// Puts an object in the cache, possibly evicting older entries if the
/// cache exceeds its maximum size. Note that, although old objects may
/// be evicted, the object just added to the cache with this function
/// will not be evicted before the next call to `put` or `deinit` even if
/// it exceeds the maximum cache size.
fn put(cache: *ObjectCache, allocator: Allocator, offset: u64, object: Object) !void {
const lru_node = try allocator.create(LruListNode);
errdefer allocator.destroy(lru_node);
lru_node.data = offset;
const gop = try cache.objects.getOrPut(allocator, offset);
if (gop.found_existing) {
cache.byte_size -= gop.value_ptr.object.data.len;
cache.lru_nodes.remove(&gop.value_ptr.lru_node.node);
cache.lru_nodes_len -= 1;
allocator.destroy(gop.value_ptr.lru_node);
allocator.free(gop.value_ptr.object.data);
}
gop.value_ptr.* = .{ .object = object, .lru_node = lru_node };
cache.byte_size += object.data.len;
cache.lru_nodes.append(&lru_node.node);
cache.lru_nodes_len += 1;
while (cache.byte_size > max_byte_size and cache.lru_nodes_len > 1) {
// The > 1 check is to make sure that we don't evict the most
// recently added node, even if it by itself happens to exceed the
// maximum size of the cache.
const evict_node: *LruListNode = @alignCast(@fieldParentPtr("node", cache.lru_nodes.popFirst().?));
cache.lru_nodes_len -= 1;
const evict_offset = evict_node.data;
allocator.destroy(evict_node);
const evict_object = cache.objects.get(evict_offset).?.object;
cache.byte_size -= evict_object.data.len;
allocator.free(evict_object.data);
_ = cache.objects.remove(evict_offset);
}
}
};
/// A single pkt-line in the Git protocol.
///
/// The format of a pkt-line is documented in
/// [protocol-common](https://git-scm.com/docs/protocol-common). The special
/// meanings of the delimiter and response-end packets are documented in
/// [protocol-v2](https://git-scm.com/docs/protocol-v2).
pub const Packet = union(enum) {
flush,
delimiter,
response_end,
data: []const u8,
pub const max_data_length = 65516;
/// Reads a packet in pkt-line format.
fn read(reader: *Io.Reader) !Packet {
const packet: Packet = try .peek(reader);
switch (packet) {
.data => |data| reader.toss(data.len),
else => {},
}
return packet;
}
/// Consumes the header of a pkt-line packet and reads any associated data
/// into the reader's buffer, but does not consume the data.
fn peek(reader: *Io.Reader) !Packet {
const length = std.fmt.parseUnsigned(u16, try reader.take(4), 16) catch return error.InvalidPacket;
switch (length) {
0 => return .flush,
1 => return .delimiter,
2 => return .response_end,
3 => return error.InvalidPacket,
else => if (length - 4 > max_data_length) return error.InvalidPacket,
}
return .{ .data = try reader.peek(length - 4) };
}
/// Writes a packet in pkt-line format.
fn write(packet: Packet, writer: *Io.Writer) !void {
switch (packet) {
.flush => try writer.writeAll("0000"),
.delimiter => try writer.writeAll("0001"),
.response_end => try writer.writeAll("0002"),
.data => |data| {
assert(data.len <= max_data_length);
try writer.print("{x:0>4}", .{data.len + 4});
try writer.writeAll(data);
},
}
}
/// Returns the normalized form of textual packet data, stripping any
/// trailing '\n'.
///
/// As documented in
/// [protocol-common](https://git-scm.com/docs/protocol-common#_pkt_line_format),
/// non-binary (textual) pkt-line data should contain a trailing '\n', but
/// is not required to do so (implementations must support both forms).
fn normalizeText(data: []const u8) []const u8 {
return if (mem.endsWith(u8, data, "\n"))
data[0 .. data.len - 1]
else
data;
}
};
/// A client session for the Git protocol, currently limited to an HTTP(S)
/// transport. Only protocol version 2 is supported, as documented in
/// [protocol-v2](https://git-scm.com/docs/protocol-v2).
pub const Session = struct {
transport: *std.http.Client,
location: Location,
supports_agent: bool,
supports_shallow: bool,
object_format: Oid.Format,
arena: Allocator,
const agent = "zig/" ++ @import("builtin").zig_version_string;
const agent_capability = std.fmt.comptimePrint("agent={s}\n", .{agent});
/// Initializes a client session and discovers the capabilities of the
/// server for optimal transport.
pub fn init(
arena: Allocator,
transport: *std.http.Client,
uri: std.Uri,
/// Asserted to be at least `Packet.max_data_length`
response_buffer: []u8,
) !Session {
assert(response_buffer.len >= Packet.max_data_length);
var session: Session = .{
.transport = transport,
.location = try .init(arena, uri),
.supports_agent = false,
.supports_shallow = false,
.object_format = .sha1,
.arena = arena,
};
var capability_iterator: CapabilityIterator = undefined;
try session.getCapabilities(&capability_iterator, response_buffer);
defer capability_iterator.deinit();
while (try capability_iterator.next()) |capability| {
if (mem.eql(u8, capability.key, "agent")) {
session.supports_agent = true;
} else if (mem.eql(u8, capability.key, "fetch")) {
var feature_iterator = mem.splitScalar(u8, capability.value orelse continue, ' ');
while (feature_iterator.next()) |feature| {
if (mem.eql(u8, feature, "shallow")) {
session.supports_shallow = true;
}
}
} else if (mem.eql(u8, capability.key, "object-format")) {
if (std.meta.stringToEnum(Oid.Format, capability.value orelse continue)) |format| {
session.object_format = format;
}
}
}
return session;
}
/// An owned `std.Uri` representing the location of the server (base URI).
const Location = struct {
uri: std.Uri,
fn init(arena: Allocator, uri: std.Uri) !Location {
const scheme = try arena.dupe(u8, uri.scheme);
const user = if (uri.user) |user| try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(user, .formatUser),
}) else null;
const password = if (uri.password) |password| try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(password, .formatPassword),
}) else null;
const host = if (uri.host) |host| try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(host, .formatHost),
}) else null;
const path = try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(uri.path, .formatPath),
});
// The query and fragment are not used as part of the base server URI.
return .{
.uri = .{
.scheme = scheme,
.user = if (user) |s| .{ .percent_encoded = s } else null,
.password = if (password) |s| .{ .percent_encoded = s } else null,
.host = if (host) |s| .{ .percent_encoded = s } else null,
.port = uri.port,
.path = .{ .percent_encoded = path },
},
};
}
};
/// Returns an iterator over capabilities supported by the server.
///
/// The `session.location` is updated if the server returns a redirect, so
/// that subsequent session functions do not need to handle redirects.
fn getCapabilities(session: *Session, it: *CapabilityIterator, response_buffer: []u8) !void {
const arena = session.arena;
assert(response_buffer.len >= Packet.max_data_length);
var info_refs_uri = session.location.uri;
{
const session_uri_path = try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(session.location.uri.path, .formatPath),
});
info_refs_uri.path = .{ .percent_encoded = try std.fs.path.resolvePosix(arena, &.{
"/", session_uri_path, "info/refs",
}) };
}
info_refs_uri.query = .{ .percent_encoded = "service=git-upload-pack" };
info_refs_uri.fragment = null;
const max_redirects = 3;
it.* = .{
.request = try session.transport.request(.GET, info_refs_uri, .{
.redirect_behavior = .init(max_redirects),
.extra_headers = &.{
.{ .name = "Git-Protocol", .value = "version=2" },
},
}),
.reader = undefined,
.decompress = undefined,
};
errdefer it.deinit();
const request = &it.request;
try request.sendBodiless();
var redirect_buffer: [1024]u8 = undefined;
var response = try request.receiveHead(&redirect_buffer);
if (response.head.status != .ok) return error.ProtocolError;
const any_redirects_occurred = request.redirect_behavior.remaining() < max_redirects;
if (any_redirects_occurred) {
const request_uri_path = try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(request.uri.path, .formatPath),
});
if (!mem.endsWith(u8, request_uri_path, "/info/refs")) return error.UnparseableRedirect;
var new_uri = request.uri;
new_uri.path = .{ .percent_encoded = request_uri_path[0 .. request_uri_path.len - "/info/refs".len] };
session.location = try .init(arena, new_uri);
}
const decompress_buffer = try arena.alloc(u8, response.head.content_encoding.minBufferCapacity());
it.reader = response.readerDecompressing(response_buffer, &it.decompress, decompress_buffer);
var state: enum { response_start, response_content } = .response_start;
while (true) {
// Some Git servers (at least GitHub) include an additional
// '# service=git-upload-pack' informative response before sending
// the expected 'version 2' packet and capability information.
// This is not universal: SourceHut, for example, does not do this.
// Thus, we need to skip any such useless additional responses
// before we get the one we're actually looking for. The responses
// will be delimited by flush packets.
const packet = Packet.read(it.reader) catch |err| switch (err) {
error.EndOfStream => return error.UnsupportedProtocol, // 'version 2' packet not found
else => |e| return e,
};
switch (packet) {
.flush => state = .response_start,
.data => |data| switch (state) {
.response_start => if (mem.eql(u8, Packet.normalizeText(data), "version 2")) {
return;
} else {
state = .response_content;
},
else => {},
},
else => return error.UnexpectedPacket,
}
}
}
const CapabilityIterator = struct {
request: std.http.Client.Request,
reader: *Io.Reader,
decompress: std.http.Decompress,
const Capability = struct {
key: []const u8,
value: ?[]const u8 = null,
fn parse(data: []const u8) Capability {
return if (mem.indexOfScalar(u8, data, '=')) |separator_pos|
.{ .key = data[0..separator_pos], .value = data[separator_pos + 1 ..] }
else
.{ .key = data };
}
};
fn deinit(it: *CapabilityIterator) void {
it.request.deinit();
it.* = undefined;
}
fn next(it: *CapabilityIterator) !?Capability {
switch (try Packet.read(it.reader)) {
.flush => return null,
.data => |data| return Capability.parse(Packet.normalizeText(data)),
else => return error.UnexpectedPacket,
}
}
};
const ListRefsOptions = struct {
/// The ref prefixes (if any) to use to filter the refs available on the
/// server. Note that the client must still check the returned refs
/// against its desired filters itself: the server is not required to
/// respect these prefix filters and may return other refs as well.
ref_prefixes: []const []const u8 = &.{},
/// Whether to include symref targets for returned symbolic refs.
include_symrefs: bool = false,
/// Whether to include the peeled object ID for returned tag refs.
include_peeled: bool = false,
/// Asserted to be at least `Packet.max_data_length`.
buffer: []u8,
};
/// Returns an iterator over refs known to the server.
pub fn listRefs(session: Session, it: *RefIterator, options: ListRefsOptions) !void {
const arena = session.arena;
assert(options.buffer.len >= Packet.max_data_length);
var upload_pack_uri = session.location.uri;
{
const session_uri_path = try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(session.location.uri.path, .formatPath),
});
upload_pack_uri.path = .{ .percent_encoded = try std.fs.path.resolvePosix(arena, &.{ "/", session_uri_path, "git-upload-pack" }) };
}
upload_pack_uri.query = null;
upload_pack_uri.fragment = null;
var body: Io.Writer = .fixed(options.buffer);
try Packet.write(.{ .data = "command=ls-refs\n" }, &body);
if (session.supports_agent) {
try Packet.write(.{ .data = agent_capability }, &body);
}
{
const object_format_packet = try std.fmt.allocPrint(arena, "object-format={t}\n", .{
session.object_format,
});
try Packet.write(.{ .data = object_format_packet }, &body);
}
try Packet.write(.delimiter, &body);
for (options.ref_prefixes) |ref_prefix| {
const ref_prefix_packet = try std.fmt.allocPrint(arena, "ref-prefix {s}\n", .{ref_prefix});
try Packet.write(.{ .data = ref_prefix_packet }, &body);
}
if (options.include_symrefs) {
try Packet.write(.{ .data = "symrefs\n" }, &body);
}
if (options.include_peeled) {
try Packet.write(.{ .data = "peel\n" }, &body);
}
try Packet.write(.flush, &body);
it.* = .{
.request = try session.transport.request(.POST, upload_pack_uri, .{
.redirect_behavior = .unhandled,
.extra_headers = &.{
.{ .name = "Content-Type", .value = "application/x-git-upload-pack-request" },
.{ .name = "Git-Protocol", .value = "version=2" },
},
}),
.reader = undefined,
.format = session.object_format,
.decompress = undefined,
};
const request = &it.request;
errdefer request.deinit();
try request.sendBodyComplete(body.buffered());
var response = try request.receiveHead(options.buffer);
if (response.head.status != .ok) return error.ProtocolError;
const decompress_buffer = try arena.alloc(u8, response.head.content_encoding.minBufferCapacity());
it.reader = response.readerDecompressing(options.buffer, &it.decompress, decompress_buffer);
}
pub const RefIterator = struct {
format: Oid.Format,
request: std.http.Client.Request,
reader: *Io.Reader,
decompress: std.http.Decompress,
pub const Ref = struct {
oid: Oid,
name: []const u8,
symref_target: ?[]const u8,
peeled: ?Oid,
};
pub fn deinit(iterator: *RefIterator) void {
iterator.request.deinit();
iterator.* = undefined;
}
pub fn next(it: *RefIterator) !?Ref {
switch (try Packet.read(it.reader)) {
.flush => return null,
.data => |data| {
const ref_data = Packet.normalizeText(data);
const oid_sep_pos = mem.indexOfScalar(u8, ref_data, ' ') orelse return error.InvalidRefPacket;
const oid = Oid.parse(it.format, data[0..oid_sep_pos]) catch return error.InvalidRefPacket;
const name_sep_pos = mem.indexOfScalarPos(u8, ref_data, oid_sep_pos + 1, ' ') orelse ref_data.len;
const name = ref_data[oid_sep_pos + 1 .. name_sep_pos];
var symref_target: ?[]const u8 = null;
var peeled: ?Oid = null;
var last_sep_pos = name_sep_pos;
while (last_sep_pos < ref_data.len) {
const next_sep_pos = mem.indexOfScalarPos(u8, ref_data, last_sep_pos + 1, ' ') orelse ref_data.len;
const attribute = ref_data[last_sep_pos + 1 .. next_sep_pos];
if (mem.startsWith(u8, attribute, "symref-target:")) {
symref_target = attribute["symref-target:".len..];
} else if (mem.startsWith(u8, attribute, "peeled:")) {
peeled = Oid.parse(it.format, attribute["peeled:".len..]) catch return error.InvalidRefPacket;
}
last_sep_pos = next_sep_pos;
}
return .{ .oid = oid, .name = name, .symref_target = symref_target, .peeled = peeled };
},
else => return error.UnexpectedPacket,
}
}
};
/// Fetches the given refs from the server. A shallow fetch (depth 1) is
/// performed if the server supports it.
pub fn fetch(
session: Session,
fs: *FetchStream,
wants: []const []const u8,
/// Asserted to be at least `Packet.max_data_length`.
response_buffer: []u8,
) !void {
const arena = session.arena;
assert(response_buffer.len >= Packet.max_data_length);
var upload_pack_uri = session.location.uri;
{
const session_uri_path = try std.fmt.allocPrint(arena, "{f}", .{
std.fmt.alt(session.location.uri.path, .formatPath),
});
upload_pack_uri.path = .{ .percent_encoded = try std.fs.path.resolvePosix(arena, &.{ "/", session_uri_path, "git-upload-pack" }) };
}
upload_pack_uri.query = null;
upload_pack_uri.fragment = null;
var body: Io.Writer = .fixed(response_buffer);
try Packet.write(.{ .data = "command=fetch\n" }, &body);
if (session.supports_agent) {
try Packet.write(.{ .data = agent_capability }, &body);
}
{
const object_format_packet = try std.fmt.allocPrint(arena, "object-format={s}\n", .{@tagName(session.object_format)});
try Packet.write(.{ .data = object_format_packet }, &body);
}
try Packet.write(.delimiter, &body);
// Our packfile parser supports the OFS_DELTA object type
try Packet.write(.{ .data = "ofs-delta\n" }, &body);
// We do not currently convey server progress information to the user
try Packet.write(.{ .data = "no-progress\n" }, &body);
if (session.supports_shallow) {
try Packet.write(.{ .data = "deepen 1\n" }, &body);
}
for (wants) |want| {
var buf: [Packet.max_data_length]u8 = undefined;
const arg = std.fmt.bufPrint(&buf, "want {s}\n", .{want}) catch unreachable;
try Packet.write(.{ .data = arg }, &body);
}
try Packet.write(.{ .data = "done\n" }, &body);
try Packet.write(.flush, &body);
fs.* = .{
.request = try session.transport.request(.POST, upload_pack_uri, .{
.redirect_behavior = .not_allowed,
.extra_headers = &.{
.{ .name = "Content-Type", .value = "application/x-git-upload-pack-request" },
.{ .name = "Git-Protocol", .value = "version=2" },
},
}),
.input = undefined,
.reader = undefined,
.remaining_len = undefined,
.decompress = undefined,
};
const request = &fs.request;
errdefer request.deinit();
try request.sendBodyComplete(body.buffered());
var response = try request.receiveHead(&.{});
if (response.head.status != .ok) return error.ProtocolError;
const decompress_buffer = try arena.alloc(u8, response.head.content_encoding.minBufferCapacity());
const reader = response.readerDecompressing(response_buffer, &fs.decompress, decompress_buffer);
// We are not interested in any of the sections of the returned fetch
// data other than the packfile section, since we aren't doing anything
// complex like ref negotiation (this is a fresh clone).
var state: enum { section_start, section_content } = .section_start;
while (true) {
const packet = try Packet.read(reader);
switch (state) {
.section_start => switch (packet) {
.data => |data| if (mem.eql(u8, Packet.normalizeText(data), "packfile")) {
fs.input = reader;
fs.reader = .{
.buffer = &.{},
.vtable = &.{ .stream = FetchStream.stream },
.seek = 0,
.end = 0,
};
fs.remaining_len = 0;
return;
} else {
state = .section_content;
},
else => return error.UnexpectedPacket,
},
.section_content => switch (packet) {
.delimiter => state = .section_start,
.data => {},
else => return error.UnexpectedPacket,
},
}
}
}
pub const FetchStream = struct {
request: std.http.Client.Request,
input: *Io.Reader,
reader: Io.Reader,
err: ?Error = null,
remaining_len: usize,
decompress: std.http.Decompress,
pub fn deinit(fs: *FetchStream) void {
fs.request.deinit();
}
pub const Error = error{
InvalidPacket,
ProtocolError,
UnexpectedPacket,
WriteFailed,
ReadFailed,
EndOfStream,
};
const StreamCode = enum(u8) {
pack_data = 1,
progress = 2,
fatal_error = 3,
_,
};
pub fn stream(r: *Io.Reader, w: *Io.Writer, limit: Io.Limit) Io.Reader.StreamError!usize {
const fs: *FetchStream = @alignCast(@fieldParentPtr("reader", r));
const input = fs.input;
if (fs.remaining_len == 0) {
while (true) {
switch (Packet.peek(input) catch |err| {
fs.err = err;
return error.ReadFailed;
}) {
.flush => return error.EndOfStream,
.data => |data| switch (@as(StreamCode, @fromBackingInt(@intCast(data[0])))) {
.pack_data => {
input.toss(1);
fs.remaining_len = data.len - 1;
break;
},
.fatal_error => {
fs.err = error.ProtocolError;
return error.ReadFailed;
},
else => {
input.toss(data.len);
},
},
else => {
fs.err = error.UnexpectedPacket;
return error.ReadFailed;
},
}
}
}
const buf = limit.slice(try w.writableSliceGreedy(1));
const n = @min(buf.len, fs.remaining_len);
try input.readSliceAll(buf[0..n]);
w.advance(n);
fs.remaining_len -= n;
return n;
}
};
};
const PackHeader = struct {
total_objects: u32,
const signature = "PACK";
const supported_version = 2;
fn read(reader: *Io.Reader) !PackHeader {
const actual_signature = reader.take(4) catch |e| switch (e) {
error.EndOfStream => return error.InvalidHeader,
else => |other| return other,
};
if (!mem.eql(u8, actual_signature, signature)) return error.InvalidHeader;
const version = reader.takeInt(u32, .big) catch |e| switch (e) {
error.EndOfStream => return error.InvalidHeader,
else => |other| return other,
};
if (version != supported_version) return error.UnsupportedVersion;
const total_objects = reader.takeInt(u32, .big) catch |e| switch (e) {
error.EndOfStream => return error.InvalidHeader,
else => |other| return other,
};
return .{ .total_objects = total_objects };
}
};
const EntryHeader = union(Type) {
commit: Undeltified,
tree: Undeltified,
blob: Undeltified,
tag: Undeltified,
ofs_delta: OfsDelta,
ref_delta: RefDelta,
const Type = enum(u3) {
commit = 1,
tree = 2,
blob = 3,
tag = 4,
ofs_delta = 6,
ref_delta = 7,
};
const Undeltified = struct {
uncompressed_length: u64,
};
const OfsDelta = struct {
offset: u64,
uncompressed_length: u64,
};
const RefDelta = struct {
base_object: Oid,
uncompressed_length: u64,
};
fn objectType(header: EntryHeader) Object.Type {
return switch (header) {
inline .commit, .tree, .blob, .tag => |_, tag| @field(Object.Type, @tagName(tag)),
else => unreachable,
};
}
fn uncompressedLength(header: EntryHeader) u64 {
return switch (header) {
inline else => |entry| entry.uncompressed_length,
};
}
fn read(format: Oid.Format, reader: *Io.Reader) !EntryHeader {
const InitialByte = packed struct { len: u4, type: u3, has_next: bool };
const initial: InitialByte = @bitCast(reader.takeByte() catch |e| switch (e) {
error.EndOfStream => return error.InvalidFormat,
else => |other| return other,
});
const rest_len = if (initial.has_next) try reader.takeLeb128(u64) else 0;
var uncompressed_length: u64 = initial.len;
uncompressed_length |= std.math.shlExact(u64, rest_len, 4) catch return error.InvalidFormat;
const @"type" = std.enums.fromInt(EntryHeader.Type, initial.type) orelse return error.InvalidFormat;
return switch (@"type") {
inline .commit, .tree, .blob, .tag => |tag| @unionInit(EntryHeader, @tagName(tag), .{
.uncompressed_length = uncompressed_length,
}),
.ofs_delta => .{ .ofs_delta = .{
.offset = try readOffsetVarInt(reader),
.uncompressed_length = uncompressed_length,
} },
.ref_delta => .{ .ref_delta = .{
.base_object = Oid.readBytes(format, reader) catch |e| switch (e) {
error.EndOfStream => return error.InvalidFormat,
else => |other| return other,
},
.uncompressed_length = uncompressed_length,
} },
};
}
};
fn readOffsetVarInt(r: *Io.Reader) !u64 {
const Byte = packed struct { value: u7, has_next: bool };
var b: Byte = @bitCast(try r.takeByte());
var value: u64 = b.value;
while (b.has_next) {
b = @bitCast(try r.takeByte());
value = std.math.shlExact(u64, value + 1, 7) catch return error.InvalidFormat;
value |= b.value;
}
return value;
}
const IndexHeader = struct {
fan_out_table: [256]u32,
const signature = "\xFFtOc";
const supported_version = 2;
const size = 4 + 4 + @sizeOf([256]u32);
fn read(index_header: *IndexHeader, reader: *Io.Reader) !void {
const sig = try reader.take(4);
if (!mem.eql(u8, sig, signature)) return error.InvalidHeader;
const version = try reader.takeInt(u32, .big);
if (version != supported_version) return error.UnsupportedVersion;
try reader.readSliceEndian(u32, &index_header.fan_out_table, .big);
}
};
const IndexEntry = struct {
offset: u64,
crc32: u32,
};
/// Writes out a version 2 index for the given packfile, as documented in
/// [pack-format](https://git-scm.com/docs/pack-format).
pub fn indexPack(
allocator: Allocator,
format: Oid.Format,
pack: *Io.File.Reader,
index_writer: *Io.File.Writer,
) !void {
try pack.seekTo(0);
var index_entries: std.AutoHashMapUnmanaged(Oid, IndexEntry) = .empty;
defer index_entries.deinit(allocator);
var pending_deltas: std.ArrayList(IndexEntry) = .empty;
defer pending_deltas.deinit(allocator);
const pack_checksum = try indexPackFirstPass(allocator, format, pack, &index_entries, &pending_deltas);
var cache: ObjectCache = .{};
defer cache.deinit(allocator);
var remaining_deltas = pending_deltas.items.len;
while (remaining_deltas > 0) {
var i: usize = remaining_deltas;
while (i > 0) {
i -= 1;
const delta = pending_deltas.items[i];
if (try indexPackHashDelta(allocator, format, pack, delta, index_entries, &cache)) |oid| {
try index_entries.put(allocator, oid, delta);
_ = pending_deltas.swapRemove(i);
}
}
if (pending_deltas.items.len == remaining_deltas) return error.IncompletePack;
remaining_deltas = pending_deltas.items.len;
}
var oids: std.ArrayList(Oid) = .empty;
defer oids.deinit(allocator);
try oids.ensureTotalCapacityPrecise(allocator, index_entries.count());
var index_entries_iter = index_entries.iterator();
while (index_entries_iter.next()) |entry| {
oids.appendAssumeCapacity(entry.key_ptr.*);
}
mem.sortUnstable(Oid, oids.items, {}, struct {
fn lessThan(_: void, o1: Oid, o2: Oid) bool {
return mem.lessThan(u8, o1.slice(), o2.slice());
}
}.lessThan);
var fan_out_table: [256]u32 = undefined;
var count: u32 = 0;
var fan_out_index: u8 = 0;
for (oids.items) |oid| {
const key = oid.slice()[0];
if (key > fan_out_index) {
@memset(fan_out_table[fan_out_index..key], count);
fan_out_index = key;
}
count += 1;
}
@memset(fan_out_table[fan_out_index..], count);
var index_hashed_writer = Io.Writer.hashed(&index_writer.interface, Oid.Hasher.init(format), &.{});
const writer = &index_hashed_writer.writer;
try writer.writeAll(IndexHeader.signature);
try writer.writeInt(u32, IndexHeader.supported_version, .big);
for (fan_out_table) |fan_out_entry| {
try writer.writeInt(u32, fan_out_entry, .big);
}
for (oids.items) |oid| {
try writer.writeAll(oid.slice());
}
for (oids.items) |oid| {
try writer.writeInt(u32, index_entries.get(oid).?.crc32, .big);
}
var big_offsets: std.ArrayList(u64) = .empty;
defer big_offsets.deinit(allocator);
for (oids.items) |oid| {
const offset = index_entries.get(oid).?.offset;
if (offset <= std.math.maxInt(u31)) {
try writer.writeInt(u32, @intCast(offset), .big);
} else {
const index = big_offsets.items.len;
try big_offsets.append(allocator, offset);
try writer.writeInt(u32, @as(u32, @intCast(index)) | (1 << 31), .big);
}
}
for (big_offsets.items) |offset| {
try writer.writeInt(u64, offset, .big);
}
try writer.writeAll(pack_checksum.slice());
const index_checksum = index_hashed_writer.hasher.finalResult();
try index_writer.interface.writeAll(index_checksum.slice());
try index_writer.end();
}
/// Performs the first pass over the packfile data for index construction.
/// This will index all non-delta objects, queue delta objects for further
/// processing, and return the pack checksum (which is part of the index
/// format).
fn indexPackFirstPass(
allocator: Allocator,
format: Oid.Format,
pack: *Io.File.Reader,
index_entries: *std.AutoHashMapUnmanaged(Oid, IndexEntry),
pending_deltas: *std.ArrayList(IndexEntry),
) !Oid {
var flate_buffer: [std.compress.flate.max_window_len]u8 = undefined;
var pack_buffer: [2048]u8 = undefined; // Reasonably large buffer for file system.
var pack_hashed = pack.interface.hashed(Oid.Hasher.init(format), &pack_buffer);
const pack_header = try PackHeader.read(&pack_hashed.reader);
for (0..pack_header.total_objects) |_| {
const entry_offset = pack.logicalPos() - pack_hashed.reader.bufferedLen();
const entry_header = try EntryHeader.read(format, &pack_hashed.reader);
switch (entry_header) {
.commit, .tree, .blob, .tag => |object| {
var entry_decompress: std.compress.flate.Decompress = .init(&pack_hashed.reader, .zlib, &.{});
var oid_hasher: Oid.Hashing = .init(format, &flate_buffer);
const oid_hasher_w = oid_hasher.writer();
// The object header is not included in the pack data but is
// part of the object's ID
try oid_hasher_w.print("{t} {d}\x00", .{ entry_header, object.uncompressed_length });
const n = try entry_decompress.reader.streamRemaining(oid_hasher_w);
if (n != object.uncompressed_length) return error.InvalidObject;
const oid = oid_hasher.final();
if (!skip_checksums) @compileError("TODO");
try index_entries.put(allocator, oid, .{
.offset = entry_offset,
.crc32 = 0,
});
},
inline .ofs_delta, .ref_delta => |delta| {
var entry_decompress: std.compress.flate.Decompress = .init(&pack_hashed.reader, .zlib, &flate_buffer);
const n = try entry_decompress.reader.discardRemaining();
if (n != delta.uncompressed_length) return error.InvalidObject;
if (!skip_checksums) @compileError("TODO");
try pending_deltas.append(allocator, .{
.offset = entry_offset,
.crc32 = 0,
});
},
}
}
if (!skip_checksums) @compileError("TODO");
return pack_hashed.hasher.finalResult();
}
/// Attempts to determine the final object ID of the given deltified object.
/// May return null if this is not yet possible (if the delta is a ref-based
/// delta and we do not yet know the offset of the base object).
fn indexPackHashDelta(
allocator: Allocator,
format: Oid.Format,
pack: *Io.File.Reader,
delta: IndexEntry,
index_entries: std.AutoHashMapUnmanaged(Oid, IndexEntry),
cache: *ObjectCache,
) !?Oid {
// Figure out the chain of deltas to resolve
var base_offset = delta.offset;
var base_header: EntryHeader = undefined;
var delta_offsets: std.ArrayList(u64) = .empty;
defer delta_offsets.deinit(allocator);
const base_object = while (true) {
if (cache.get(base_offset)) |base_object| break base_object;
try pack.seekTo(base_offset);
base_header = try EntryHeader.read(format, &pack.interface);
switch (base_header) {
.ofs_delta => |ofs_delta| {
try delta_offsets.append(allocator, base_offset);
base_offset = std.math.sub(u64, base_offset, ofs_delta.offset) catch return error.InvalidObject;
},
.ref_delta => |ref_delta| {
try delta_offsets.append(allocator, base_offset);
base_offset = (index_entries.get(ref_delta.base_object) orelse return null).offset;
},
else => {
const base_data = try readObjectRaw(allocator, &pack.interface, base_header.uncompressedLength());
errdefer allocator.free(base_data);
const base_object: Object = .{ .type = base_header.objectType(), .data = base_data };
try cache.put(allocator, base_offset, base_object);
break base_object;
},
}
};
const base_data = try resolveDeltaChain(allocator, format, pack, base_object, delta_offsets.items, cache);
var entry_hasher_buffer: [64]u8 = undefined;
var entry_hasher: Oid.Hashing = .init(format, &entry_hasher_buffer);
const entry_hasher_w = entry_hasher.writer();
// Writes to hashers cannot fail.
entry_hasher_w.print("{t} {d}\x00", .{ base_object.type, base_data.len }) catch unreachable;
entry_hasher_w.writeAll(base_data) catch unreachable;
return entry_hasher.final();
}
/// Resolves a chain of deltas, returning the final base object data. `pack` is
/// assumed to be looking at the start of the object data for the base object of
/// the chain, and will then apply the deltas in `delta_offsets` in reverse order
/// to obtain the final object.
fn resolveDeltaChain(
allocator: Allocator,
format: Oid.Format,
pack: *Io.File.Reader,
base_object: Object,
delta_offsets: []const u64,
cache: *ObjectCache,
) ![]const u8 {
var base_data = base_object.data;
var i: usize = delta_offsets.len;
while (i > 0) {
i -= 1;
const delta_offset = delta_offsets[i];
try pack.seekTo(delta_offset);
const delta_header = try EntryHeader.read(format, &pack.interface);
const delta_data = try readObjectRaw(allocator, &pack.interface, delta_header.uncompressedLength());
defer allocator.free(delta_data);
var delta_reader: Io.Reader = .fixed(delta_data);
_ = try delta_reader.takeLeb128(u64); // base object size
const expanded_size = try delta_reader.takeLeb128(u64);
const expanded_alloc_size = std.math.cast(usize, expanded_size) orelse return error.ObjectTooLarge;
const expanded_data = try allocator.alloc(u8, expanded_alloc_size);
errdefer allocator.free(expanded_data);
var expanded_delta_stream: Io.Writer = .fixed(expanded_data);
try expandDelta(base_data, &delta_reader, &expanded_delta_stream);
if (expanded_delta_stream.end != expanded_size) return error.InvalidObject;
try cache.put(allocator, delta_offset, .{ .type = base_object.type, .data = expanded_data });
base_data = expanded_data;
}
return base_data;
}
/// Reads the complete contents of an object from `reader`. This function may
/// read more bytes than required from `reader`, so the reader position after
/// returning is not reliable.
fn readObjectRaw(allocator: Allocator, reader: *Io.Reader, size: u64) ![]u8 {
const alloc_size = std.math.cast(usize, size) orelse return error.ObjectTooLarge;
var aw: Io.Writer.Allocating = .init(allocator);
try aw.ensureTotalCapacity(alloc_size + std.compress.flate.max_window_len);
defer aw.deinit();
var decompress: std.compress.flate.Decompress = .init(reader, .zlib, &.{});
try decompress.reader.streamExact(&aw.writer, alloc_size);
return aw.toOwnedSlice();
}
/// Expands delta data from `delta_reader` to `writer`.
///
/// The format of the delta data is documented in
/// [pack-format](https://git-scm.com/docs/pack-format).
fn expandDelta(base_object: []const u8, delta_reader: *Io.Reader, writer: *Io.Writer) !void {
while (true) {
const inst: packed struct { value: u7, copy: bool } = @bitCast(delta_reader.takeByte() catch |e| switch (e) {
error.EndOfStream => return,
else => |other| return other,
});
if (inst.copy) {
const available: packed struct {
offset1: bool,
offset2: bool,
offset3: bool,
offset4: bool,
size1: bool,
size2: bool,
size3: bool,
} = @bitCast(inst.value);
const offset_parts: packed struct { offset1: u8, offset2: u8, offset3: u8, offset4: u8 } = .{
.offset1 = if (available.offset1) try delta_reader.takeByte() else 0,
.offset2 = if (available.offset2) try delta_reader.takeByte() else 0,
.offset3 = if (available.offset3) try delta_reader.takeByte() else 0,
.offset4 = if (available.offset4) try delta_reader.takeByte() else 0,
};
const base_offset: u32 = @bitCast(offset_parts);
const size_parts: packed struct { size1: u8, size2: u8, size3: u8 } = .{
.size1 = if (available.size1) try delta_reader.takeByte() else 0,
.size2 = if (available.size2) try delta_reader.takeByte() else 0,
.size3 = if (available.size3) try delta_reader.takeByte() else 0,
};
var size: u24 = @bitCast(size_parts);
if (size == 0) size = 0x10000;
try writer.writeAll(base_object[base_offset..][0..size]);
} else if (inst.value != 0) {
try delta_reader.streamExact(writer, inst.value);
} else {
return error.InvalidDeltaInstruction;
}
}
}
/// Runs the packfile indexing and checkout test.
///
/// The two testrepo repositories under testdata contain identical commit
/// histories and contents.
///
/// To verify the contents of the packfiles using Git alone, run the
/// following commands in an empty directory:
///
/// 1. `git init --object-format=(sha1|sha256)`
/// 2. `git unpack-objects <path/to/testrepo.pack`
/// 3. `git fsck` - will print one "dangling commit":
/// - SHA-1: `dd582c0720819ab7130b103635bd7271b9fd4feb`
/// - SHA-256: `7f444a92bd4572ee4a28b2c63059924a9ca1829138553ef3e7c41ee159afae7a`
/// 4. `git checkout $commit`
fn runRepositoryTest(io: Io, comptime format: Oid.Format, head_commit: []const u8) !void {
const testrepo_pack = @embedFile("git/testdata/testrepo-" ++ @tagName(format) ++ ".pack");
var git_dir = testing.tmpDir(.{});
defer git_dir.cleanup();
var pack_file = try git_dir.dir.createFile(io, "testrepo.pack", .{ .read = true });
defer pack_file.close(io);
try pack_file.writeStreamingAll(io, testrepo_pack);
var pack_file_buffer: [2000]u8 = undefined;
var pack_file_reader = pack_file.reader(io, &pack_file_buffer);
var index_file = try git_dir.dir.createFile(io, "testrepo.idx", .{ .read = true });
defer index_file.close(io);
var index_file_buffer: [2000]u8 = undefined;
var index_file_writer = index_file.writer(io, &index_file_buffer);
try indexPack(testing.allocator, format, &pack_file_reader, &index_file_writer);
// Arbitrary size limit on files read while checking the repository contents
// (all files in the test repo are known to be smaller than this)
const max_file_size = 8192;
if (!skip_checksums) {
const index_file_data = try git_dir.dir.readFileAlloc(io, "testrepo.idx", testing.allocator, .limited(max_file_size));
defer testing.allocator.free(index_file_data);
// testrepo.idx is generated by Git. The index created by this file should
// match it exactly. Running `git verify-pack -v testrepo.pack` can verify
// this.
const testrepo_idx = @embedFile("git/testdata/testrepo-" ++ @tagName(format) ++ ".idx");
try testing.expectEqualSlices(u8, testrepo_idx, index_file_data);
}
var index_file_reader = index_file.reader(io, &index_file_buffer);
var repository: Repository = undefined;
try repository.init(testing.allocator, format, &pack_file_reader, &index_file_reader);
defer repository.deinit();
var worktree = testing.tmpDir(.{ .iterate = true });
defer worktree.cleanup();
const commit_id = try Oid.parse(format, head_commit);
var diagnostics: Diagnostics = .{ .allocator = testing.allocator };
defer diagnostics.deinit();
try repository.checkout(io, worktree.dir, commit_id, &diagnostics);
try testing.expect(diagnostics.errors.items.len == 0);
const expected_files: []const []const u8 = &.{
"dir/file",
"dir/subdir/file",
"dir/subdir/file2",
"dir2/file",
"dir3/file",
"dir3/file2",
"file",
"file2",
"file3",
"file4",
"file5",
"file6",
"file7",
"file8",
"file9",
};
var actual_files: std.ArrayList([]u8) = .empty;
defer actual_files.deinit(testing.allocator);
defer for (actual_files.items) |file| testing.allocator.free(file);
var walker = try worktree.dir.walk(testing.allocator);
defer walker.deinit();
while (try walker.next(io)) |entry| {
if (entry.kind != .file) continue;
const path = try testing.allocator.dupe(u8, entry.path);
errdefer testing.allocator.free(path);
mem.replaceScalar(u8, path, std.fs.path.sep, '/');
try actual_files.append(testing.allocator, path);
}
mem.sortUnstable([]u8, actual_files.items, {}, struct {
fn lessThan(_: void, a: []u8, b: []u8) bool {
return mem.lessThan(u8, a, b);
}
}.lessThan);
try testing.expectEqualDeep(expected_files, actual_files.items);
const expected_file_contents =
\\revision 1
\\revision 2
\\revision 4
\\revision 5
\\revision 7
\\revision 8
\\revision 9
\\revision 10
\\revision 12
\\revision 13
\\revision 14
\\revision 18
\\revision 19
\\
;
const actual_file_contents = try worktree.dir.readFileAlloc(io, "file", testing.allocator, .limited(max_file_size));
defer testing.allocator.free(actual_file_contents);
try testing.expectEqualStrings(expected_file_contents, actual_file_contents);
}
/// Checksum calculation is useful for troubleshooting and debugging, but it's
/// redundant since the package manager already does content hashing at the
/// end. Let's save time by not doing that work, but, I left a cookie crumb
/// trail here if you want to restore the functionality for tinkering purposes.
const skip_checksums = true;
test "SHA-1 packfile indexing and checkout" {
try runRepositoryTest(std.testing.io, .sha1, "dd582c0720819ab7130b103635bd7271b9fd4feb");
}
test "SHA-256 packfile indexing and checkout" {
try runRepositoryTest(std.testing.io, .sha256, "7f444a92bd4572ee4a28b2c63059924a9ca1829138553ef3e7c41ee159afae7a");
}
/// Checks out a commit of a packfile. Intended for experimenting with and
/// benchmarking possible optimizations to the indexing and checkout behavior.
pub fn main() !void {
const allocator = std.heap.smp_allocator;
var threaded: Io.Threaded = .init(allocator, .{});
defer threaded.deinit();
const io = threaded.io();
const args = try std.process.argsAlloc(allocator);
defer std.process.argsFree(allocator, args);
if (args.len != 5) {
return error.InvalidArguments; // Arguments: format packfile commit worktree
}
const format = std.meta.stringToEnum(Oid.Format, args[1]) orelse return error.InvalidFormat;
var pack_file = try Io.Dir.cwd().openFile(io, args[2], .{});
defer pack_file.close(io);
var pack_file_buffer: [4096]u8 = undefined;
var pack_file_reader = pack_file.reader(io, &pack_file_buffer);
const commit = try Oid.parse(format, args[3]);
var worktree = try Io.Dir.cwd().createDirPathOpen(io, args[4], .{});
defer worktree.close(io);
var git_dir = try worktree.createDirPathOpen(io, ".git", .{});
defer git_dir.close(io);
std.debug.print("Starting index...\n", .{});
var index_file = try git_dir.createFile(io, "idx", .{ .read = true });
defer index_file.close(io);
var index_file_buffer: [4096]u8 = undefined;
var index_file_writer = index_file.writer(io, &index_file_buffer);
try indexPack(allocator, format, &pack_file_reader, &index_file_writer);
std.debug.print("Starting checkout...\n", .{});
var index_file_reader = index_file.reader(io, &index_file_buffer);
var repository: Repository = undefined;
try repository.init(allocator, format, &pack_file_reader, &index_file_reader);
defer repository.deinit();
var diagnostics: Diagnostics = .{ .allocator = allocator };
defer diagnostics.deinit();
try repository.checkout(io, worktree, commit, &diagnostics);
for (diagnostics.errors.items) |err| {
std.debug.print("Diagnostic: {}\n", .{err});
}
}