Zig 0.17.0-dev (Split by item)

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Hashing

Provides a Writer implementation based on calling Hasher.update, discarding all data.

This implementation makes suboptimal buffering decisions due to being generic. A better solution will involve creating a writer for each hash function, where the splat buffer can be tailored to the hash implementation details.

The total number of bytes written is stored in hasher.

Contrast with Hashed which also passes the data to an underlying stream.

Writer.Hashing

pub fn Hashing(comptime Hasher: type) type

File

lib/std/Io/Writer.zig:2506

Code

pub fn Hashing(comptime Hasher: type) type {
    return struct {
        hasher: Hasher,
        writer: Writer,

        pub fn init(buffer: []u8) @This() {
            return .initHasher(.init(.{}), buffer);
        }

        pub fn initHasher(hasher: Hasher, buffer: []u8) @This() {
            return .{
                .hasher = hasher,
                .writer = .{
                    .buffer = buffer,
                    .vtable = &.{ .drain = @This().drain },
                },
            };
        }

        fn drain(w: *Writer, data: []const []const u8, splat: usize) Error!usize {
            const this: *@This() = @alignCast(@fieldParentPtr("writer", w));
            this.hasher.update(w.buffered());
            w.end = 0;
            var n: usize = 0;
            for (data[0 .. data.len - 1]) |slice| {
                this.hasher.update(slice);
                n += slice.len;
            }
            for (0..splat) |_| this.hasher.update(data[data.len - 1]);
            return n + splat * data[data.len - 1].len;
        }
    };
}