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const std = @import("std");
const jpg = @import("root.zig");
pub const Segment = union(enum) {
temporary: void,
reset: void,
start_of_image: void,
end_of_image: void,
jfif: jpg.Jfif,
frame: jpg.Frame,
quantization_tables: [4]?jpg.QuantizationTable,
huffman_tables: []jpg.HuffmanTable,
scan: jpg.Scan,
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{} },
.application_segment => |n| read_application_segment(reader, n),
.define_quantization_table => dqt: {
var size = try reader.takeInt(u16, .big) - 2;
var tables: [4]?jpg.QuantizationTable = .{ null, null, null, null };
while (size > 0) {
const table = try jpg.QuantizationTable.read(reader);
tables[table.identifier] = table;
size -= @truncate(table.size_in_file());
}
break :dqt .{ .quantization_tables = tables };
},
.start_of_frame => |n| sof: {
reader.toss(2);
break :sof .{ .frame = try .read(gpa, n, reader) };
},
.define_huffman_table => dhf: {
var size = try reader.takeInt(u16, .big) - 2;
var tables: std.ArrayList(jpg.HuffmanTable) = .empty;
errdefer tables.deinit(gpa);
while (size > 0) {
const table = try tables.addOne(gpa);
table.* = try .read(gpa, reader);
size -= @truncate(table.size_in_file());
}
break :dhf .{ .huffman_tables = try tables.toOwnedSlice(gpa) };
},
.start_of_scan => sos: {
reader.toss(2);
break :sos .{ .scan = try .read(gpa, reader) };
},
else => {
std.debug.panic("unimplemented tag '{s}'\n", .{@tagName(marker)});
},
};
}
fn read_application_segment(reader: *std.Io.Reader, n: usize) !Self {
return switch (n) {
0 => jfif: {
reader.toss(2);
break :jfif .{
.jfif = try .read(reader)
};
},
else => std.debug.panic("unimplemented app{}\n", .{n}),
};
}
pub fn deinit(self: *Self, gpa: std.mem.Allocator) void {
switch (self.*) {
.frame => |*frame| frame.deinit(gpa),
.huffman_tables => |tables| {
for (tables) |*table| table.deinit(gpa);
gpa.free(tables);
},
.scan => |*s| s.deinit(gpa),
else => {},
}
}
};
test "rgb" {
const buffer = @embedFile("../testing/rgb.jpg");
var reader: std.Io.Reader = .fixed(buffer);
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
try std.testing.expectEqual(.start_of_image, std.meta.activeTag(segment));
}
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
try std.testing.expectEqual(.jfif, std.meta.activeTag(segment));
}
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
const table = segment.quantization_tables[0].?;
try std.testing.expectEqual(.b8, table.precision);
try std.testing.expectEqual(0, table.identifier);
}
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
const table = segment.quantization_tables[1].?;
try std.testing.expectEqual(.b8, table.precision);
try std.testing.expectEqual(1, table.identifier);
}
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
try std.testing.expectEqual(0, segment.frame.index);
try std.testing.expectEqual(8, segment.frame.sample_precision);
try std.testing.expectEqual(450, segment.frame.number_of_lines);
try std.testing.expectEqual(600, segment.frame.samples_per_line);
try std.testing.expectEqual(3, segment.frame.components.len);
for (segment.frame.components, 0..) |component, index| {
try std.testing.expectEqual(index + 1, component.identifier);
}
}
for (0..4) |_| {
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
try std.testing.expectEqual(.huffman_tables, std.meta.activeTag(segment));
}
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
try std.testing.expectEqual(.scan, std.meta.activeTag(segment));
}
{
var segment: Segment = try .read(std.testing.allocator, &reader);
defer segment.deinit(std.testing.allocator);
try std.testing.expectEqual(.end_of_image, std.meta.activeTag(segment));
}
}
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