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more correct gpt-decoder #15

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ebb61ea
more correct gpt-decoder
sharpobject Mar 23, 2025
0dcad61
fix gpt-decode table generation to not assume little endian
sharpobject Apr 9, 2025
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345 changes: 345 additions & 0 deletions src/preprocessing/gpt_encode.zig
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Original file line number Diff line number Diff line change
@@ -0,0 +1,345 @@
const std = @import("std");
const io = std.io;

const ENCODE_TABLE: [256][]const u8 = .{
"\xc4\x80",
"\xc4\x81",
"\xc4\x82",
"\xc4\x83",
"\xc4\x84",
"\xc4\x85",
"\xc4\x86",
"\xc4\x87",
"\xc4\x88",
"\xc4\x89",
"\xc4\x8a",
"\xc4\x8b",
"\xc4\x8c",
"\xc4\x8d",
"\xc4\x8e",
"\xc4\x8f",
"\xc4\x90",
"\xc4\x91",
"\xc4\x92",
"\xc4\x93",
"\xc4\x94",
"\xc4\x95",
"\xc4\x96",
"\xc4\x97",
"\xc4\x98",
"\xc4\x99",
"\xc4\x9a",
"\xc4\x9b",
"\xc4\x9c",
"\xc4\x9d",
"\xc4\x9e",
"\xc4\x9f",
"\xc4\xa0",
"\x21",
"\x22",
"\x23",
"\x24",
"\x25",
"\x26",
"\x27",
"\x28",
"\x29",
"\x2a",
"\x2b",
"\x2c",
"\x2d",
"\x2e",
"\x2f",
"\x30",
"\x31",
"\x32",
"\x33",
"\x34",
"\x35",
"\x36",
"\x37",
"\x38",
"\x39",
"\x3a",
"\x3b",
"\x3c",
"\x3d",
"\x3e",
"\x3f",
"\x40",
"\x41",
"\x42",
"\x43",
"\x44",
"\x45",
"\x46",
"\x47",
"\x48",
"\x49",
"\x4a",
"\x4b",
"\x4c",
"\x4d",
"\x4e",
"\x4f",
"\x50",
"\x51",
"\x52",
"\x53",
"\x54",
"\x55",
"\x56",
"\x57",
"\x58",
"\x59",
"\x5a",
"\x5b",
"\x5c",
"\x5d",
"\x5e",
"\x5f",
"\x60",
"\x61",
"\x62",
"\x63",
"\x64",
"\x65",
"\x66",
"\x67",
"\x68",
"\x69",
"\x6a",
"\x6b",
"\x6c",
"\x6d",
"\x6e",
"\x6f",
"\x70",
"\x71",
"\x72",
"\x73",
"\x74",
"\x75",
"\x76",
"\x77",
"\x78",
"\x79",
"\x7a",
"\x7b",
"\x7c",
"\x7d",
"\x7e",
"\xc4\xa1",
"\xc4\xa2",
"\xc4\xa3",
"\xc4\xa4",
"\xc4\xa5",
"\xc4\xa6",
"\xc4\xa7",
"\xc4\xa8",
"\xc4\xa9",
"\xc4\xaa",
"\xc4\xab",
"\xc4\xac",
"\xc4\xad",
"\xc4\xae",
"\xc4\xaf",
"\xc4\xb0",
"\xc4\xb1",
"\xc4\xb2",
"\xc4\xb3",
"\xc4\xb4",
"\xc4\xb5",
"\xc4\xb6",
"\xc4\xb7",
"\xc4\xb8",
"\xc4\xb9",
"\xc4\xba",
"\xc4\xbb",
"\xc4\xbc",
"\xc4\xbd",
"\xc4\xbe",
"\xc4\xbf",
"\xc5\x80",
"\xc5\x81",
"\xc5\x82",
"\xc2\xa1",
"\xc2\xa2",
"\xc2\xa3",
"\xc2\xa4",
"\xc2\xa5",
"\xc2\xa6",
"\xc2\xa7",
"\xc2\xa8",
"\xc2\xa9",
"\xc2\xaa",
"\xc2\xab",
"\xc2\xac",
"\xc5\x83",
"\xc2\xae",
"\xc2\xaf",
"\xc2\xb0",
"\xc2\xb1",
"\xc2\xb2",
"\xc2\xb3",
"\xc2\xb4",
"\xc2\xb5",
"\xc2\xb6",
"\xc2\xb7",
"\xc2\xb8",
"\xc2\xb9",
"\xc2\xba",
"\xc2\xbb",
"\xc2\xbc",
"\xc2\xbd",
"\xc2\xbe",
"\xc2\xbf",
"\xc3\x80",
"\xc3\x81",
"\xc3\x82",
"\xc3\x83",
"\xc3\x84",
"\xc3\x85",
"\xc3\x86",
"\xc3\x87",
"\xc3\x88",
"\xc3\x89",
"\xc3\x8a",
"\xc3\x8b",
"\xc3\x8c",
"\xc3\x8d",
"\xc3\x8e",
"\xc3\x8f",
"\xc3\x90",
"\xc3\x91",
"\xc3\x92",
"\xc3\x93",
"\xc3\x94",
"\xc3\x95",
"\xc3\x96",
"\xc3\x97",
"\xc3\x98",
"\xc3\x99",
"\xc3\x9a",
"\xc3\x9b",
"\xc3\x9c",
"\xc3\x9d",
"\xc3\x9e",
"\xc3\x9f",
"\xc3\xa0",
"\xc3\xa1",
"\xc3\xa2",
"\xc3\xa3",
"\xc3\xa4",
"\xc3\xa5",
"\xc3\xa6",
"\xc3\xa7",
"\xc3\xa8",
"\xc3\xa9",
"\xc3\xaa",
"\xc3\xab",
"\xc3\xac",
"\xc3\xad",
"\xc3\xae",
"\xc3\xaf",
"\xc3\xb0",
"\xc3\xb1",
"\xc3\xb2",
"\xc3\xb3",
"\xc3\xb4",
"\xc3\xb5",
"\xc3\xb6",
"\xc3\xb7",
"\xc3\xb8",
"\xc3\xb9",
"\xc3\xba",
"\xc3\xbb",
"\xc3\xbc",
"\xc3\xbd",
"\xc3\xbe",
"\xc3\xbf",
};

pub fn encode(out: []u8, in: []const u8) ![]u8 {
var i: usize = 0;
var out_idx: usize = 0;
while (i < in.len) : (i += 1) {
const slice = ENCODE_TABLE[in[i]];
const end_idx = out_idx + slice.len;
if (end_idx > out.len) {
return error.YourSliceIsTooSmall;
}
@memcpy(out[out_idx..end_idx], slice);
out_idx = end_idx;
}
return out[0..out_idx];
}

pub fn get_encoded_len(in: []const u8) usize {
var i: usize = 0;
var out_idx: usize = 0;
while (i < in.len) : (i += 1) {
const slice = ENCODE_TABLE[in[i]];
out_idx += slice.len;
}
return out_idx;
}

fn make_decode_table() [0x10000]u8 {
@setEvalBranchQuota(100000);
var ret: [0x10000]u8 = undefined;
@memset(&ret, 0xaa);
for (ENCODE_TABLE, 0..) |slice, i| {
if (slice.len == 1) {
var n: usize = 0;
while (n < 256) : (n += 1) {
const idx: u16 = @bitCast([2]u8{slice[0], n});
ret[idx] = i;
}
}
if (slice.len == 2) {
const value: u16 = @bitCast((slice.ptr)[0..2].*);
ret[value] = @as(u8, @intCast(i));
}
}
return ret;
}

const DECODE_TABLE = make_decode_table();

pub fn decode(out: []u8, in: []const u8) ![]u8 {
var i: usize = 0;
var out_idx: usize = 0;
while (i < in.len) : (i += 1) {
var value: u16 = 0;
if (i+1 < in.len) {
value = @bitCast((in.ptr + i)[0..2].*);
} else {
value = in[i];
}
const out_byte = DECODE_TABLE[value];
if (out_idx >= out.len) {
return error.YourSliceIsTooSmall;
}
out[out_idx] = out_byte;
out_idx += 1;
i += (value >> 7) & 1;
}
return out[0..out_idx];
}

pub fn get_decoded_len(in: []const u8) usize {
var i: usize = 0;
var out_idx: usize = 0;
while (i < in.len) : (i += 1) {
var value: u16 = 0;
if (i+1 < in.len) {
value = @bitCast((in.ptr + i)[0..2].*);
} else {
value = in[i];
}
i += (value >> 7) & 1;
out_idx += 1;
}
return out_idx;
}
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