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const std = @import("std");
// ZIP file implementation
// See spec.txt.
const ZipFile = struct {
allocator: std.mem.Allocator,
is_zip_64: bool = false,
end_of_central_directory_record: EndOfCentralDirectoryRecord,
central_directory_headers: []CentralDirectoryHeader,
fn from(allocator: std.mem.Allocator, file_or_stream: anytype) !ZipFile {
// Find the EndOfCentralDirectoryRecord. It must be in the last 64k of the file
const eocdr_search_width_max: usize = 64_000;
const epos = try file_or_stream.getEndPos();
const eocdr_search_width: usize = @min(epos, eocdr_search_width_max);
const eocdr_seek_start: usize = epos - eocdr_search_width;
try file_or_stream.seekTo(eocdr_seek_start);
var reader = file_or_stream.reader();
const needle = @byteSwap(EndOfCentralDirectoryRecord.SIG);
var window: u32 = try reader.readIntLittle(u32);
while (true) {
if (window == needle) {
try file_or_stream.seekBy(-4);
break;
}
const nb = try reader.readByte();
window <<= 8;
window |= nb;
} else {
return error.EndOfCentralDirectoryRecordNotFound;
}
var eocdr = try EndOfCentralDirectoryRecord.read(allocator, file_or_stream);
errdefer eocdr.deinit(allocator);
if (eocdr.disk_number_this != 0 or eocdr.disk_number_central_dir_start != 0) return error.SpansNotSupported;
if (eocdr.total_central_dir_entries != eocdr.total_central_dir_entries_on_this_disk) return error.SpansNotSupported;
var central_directory_headers = try allocator.alloc(CentralDirectoryHeader, eocdr.total_central_dir_entries);
errdefer allocator.free(central_directory_headers);
try file_or_stream.seekTo(eocdr.central_dir_offset);
for (0..eocdr.total_central_dir_entries) |i| {
central_directory_headers[i] = try CentralDirectoryHeader.read(allocator, file_or_stream);
}
return ZipFile{
.allocator = allocator,
.end_of_central_directory_record = eocdr,
.central_directory_headers = central_directory_headers,
};
}
fn deinit(self: *ZipFile) void {
self.end_of_central_directory_record.deinit(self.allocator);
for (0..self.central_directory_headers.len) |i| {
self.central_directory_headers[i].deinit(self.allocator);
}
self.allocator.free(self.central_directory_headers);
}
// [local file header 1]
// [encryption header 1]
// [file data 1]
// [data descriptor 1]
// .
// .
// .
// [local file header n]
// [encryption header n]
// [file data n]
// [data descriptor n]
// [archive decryption header]
// [archive extra data record]
// [central directory header 1]
// .
// .
// .
// [central directory header n]
// [zip64 end of central directory record]
// [zip64 end of central directory locator]
// [end of central directory record]
};
const Dynamic = struct {
field_name: []const u8,
length_field_name: []const u8,
};
fn read2(
allocator: std.mem.Allocator,
stream_or_file: anytype,
comptime T: type,
comptime sig: u32,
comptime dynamics: []const Dynamic,
) !T {
const ti = @typeInfo(T);
if (ti != .Struct) @compileError("read2 expects type parameter T to be a struct, but it was a " ++ @typeName(T));
const si = ti.Struct;
var reader = stream_or_file.reader();
const sig_actual = try reader.readIntLittle(u32);
if (sig_actual != sig) {
std.log.err("invalid signature expected {x} got {x}", .{ sig, sig_actual });
return error.InvalidSignature;
}
var t: T = undefined;
inline for (si.fields) |field| {
const fti = @typeInfo(field.type);
dynamic: inline for (dynamics) |dyn| {
if (comptime std.mem.eql(u8, dyn.field_name, field.name)) {
if (fti != .Pointer) @compileError("field " ++ field.name ++ " is marked dynamic but isn't a pointer. Instead it's a " ++ @typeName(field.type));
const pi = fti.Pointer;
if (pi.size != .Slice) @compileError("field " ++ field.name ++ " is marked dynamic, but isn't a slice, instead it's sized " ++ @tagName(pi.size));
const len = @field(t, dyn.length_field_name);
var buf = try allocator.alloc(pi.child, len);
// TODO how to errdefer in a loop, not sure where the scope ends.
_ = try reader.readAll(buf);
@field(t, field.name) = buf;
break :dynamic;
}
} else {
switch (fti) {
.Int => {
@field(t, field.name) = try reader.readIntLittle(field.type);
},
else => @compileError("don't know how to handle field " ++ field.name ++ " of type " ++ @tagName(fti)),
}
}
}
return t;
}
const CentralDirectoryHeader = struct {
const SIG: u32 = @as(u32, 0x02014b50);
version_made_by: u16,
version_needed_to_extract: u16,
general_purpose_bit_flag: u16,
compression_method: u16,
last_mod_file_time: u16,
last_mod_file_date: u16,
crc32: u32,
compressed_size: u32,
uncompressed_size: u32,
file_name_length: u16,
extra_field_length: u16,
file_comment_length: u16,
disk_number_start: u16,
internal_file_attributes: u16,
external_file_attributes: u32,
relative_offset_of_local_header: u32,
file_name: []const u8,
extra_field: []const u8,
file_comment: []const u8,
fn read(allocator: std.mem.Allocator, stream_or_file: anytype) !CentralDirectoryHeader {
return read2(allocator, stream_or_file, CentralDirectoryHeader, CentralDirectoryHeader.SIG, &[_]Dynamic{
.{ .field_name = "file_name", .length_field_name = "file_name_length" },
.{ .field_name = "extra_field", .length_field_name = "extra_field_length" },
.{ .field_name = "file_comment", .length_field_name = "file_comment_length" },
});
}
fn deinit(self: *CentralDirectoryHeader, allocator: std.mem.Allocator) void {
allocator.free(self.file_name);
allocator.free(self.extra_field);
allocator.free(self.file_comment);
}
};
const EndOfCentralDirectoryRecord = struct {
const SIG: u32 = @as(u32, 0x06054b50);
disk_number_this: u16,
disk_number_central_dir_start: u16,
total_central_dir_entries_on_this_disk: u16,
total_central_dir_entries: u16,
size_of_central_dir: u32,
central_dir_offset: u32,
comment_length: u16,
comment: []const u8,
fn read(allocator: std.mem.Allocator, file_or_stream: anytype) !EndOfCentralDirectoryRecord {
return read2(allocator, file_or_stream, EndOfCentralDirectoryRecord, EndOfCentralDirectoryRecord.SIG, &[_]Dynamic{
.{ .field_name = "comment", .length_field_name = "comment_length" },
});
}
fn deinit(self: *EndOfCentralDirectoryRecord, allocator: std.mem.Allocator) void {
allocator.free(self.comment);
}
};
test "foo" {
const test_zip = @embedFile("hello.zip");
var fbs = std.io.fixedBufferStream(test_zip);
var zf = try ZipFile.from(std.testing.allocator, &fbs);
defer zf.deinit();
try std.testing.expectEqual(zf.central_directory_headers.len, 2);
try std.testing.expectEqualStrings(zf.central_directory_headers[0].file_name, "hello.txt");
try std.testing.expectEqualStrings(zf.central_directory_headers[1].file_name, "foo.txt");
}
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