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const std = @import("std");
const jpg = @import("root.zig");
pub const Segment = union(jpg.Marker.Kind) {
temporary: void,
reset: void,
start_of_image: void,
end_of_image: void,
start_of_frame: void,
define_quantization_table: void,
define_huffman_table: void,
define_restart_interval: void,
define_number_of_lines: void,
define_hierarchy_progression: void,
extend_huffman_table: void,
application_segment: void,
comment: void,
start_of_scan: void,
const Self = @This();
pub fn read(gpa: std.mem.Allocator, reader: *std.Io.Reader) !Self {
if (try reader.peekByte() != 0xff) {
return error.InvalidMarkerHeader;
}
reader.toss(1);
const marker = jpg.Marker.from_u8(try reader.peekByte())
catch return error.InvalidMarkerByte;
reader.toss(1);
return switch (marker) {
.temporary => .{ .temporary = void{} },
.reset => .{ .reset = void{} },
.start_of_image => .{ .start_of_image = void{} },
.end_of_image => .{ .end_of_image = void{} },
.start_of_frame => data: {
const buffer = try read_data_with_length(gpa, reader);
defer gpa.free(buffer);
break :data .{ .start_of_frame = void{} };
},
.application_segment => data: {
const buffer = try read_data_with_length(gpa, reader);
defer gpa.free(buffer);
break :data .{ .application_segment = void{} };
},
else => {
std.debug.panic("unimplemented tag '{s}'\n", .{@tagName(marker)});
},
};
}
fn read_data_with_length(gpa: std.mem.Allocator, reader: *std.Io.Reader) ![]u8 {
const length = try reader.takeInt(u16, .big);
return try reader.readAlloc(gpa, @intCast(length));
}
};
test "file" {
const buffer = @embedFile("../testing/rgb.jpg");
var reader: std.Io.Reader = .fixed(buffer);
var segment: Segment = try .read(std.testing.allocator, &reader);
try std.testing.expectEqual(.start_of_image, std.meta.activeTag(segment));
segment = try .read(std.testing.allocator, &reader);
try std.testing.expectEqual(.application_segment, std.meta.activeTag(segment));
}
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