slimpack/lib/fmt.c

// Similar in concept to Lua's pack and unpack
// Main differences are:
// - Some formats are reinterpreted to mean the same thing across architectures
// - Default endianness is big-endian (but that can easily be changed, of course)
// - Formats are parsed once and used many times, to reduce overhead
// - Polyfills will store packers and unpackers in weak tables
// - Default alignment is no alignment
// - The maximum size of an integer is 64 bits (instead of 128)

#include <lauxlib.h>
#include <lua.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>

#include "lib.h"

#define FMT_UDATA_NAME "fmt.meta"

typedef enum {
	FMT_INT8,
	FMT_UINT8,
	FMT_INT16,
	FMT_UINT16,
	FMT_INT32,
	FMT_UINT32,
	FMT_INT64,
	FMT_UINT64,

	FMT_FLOAT32,
	FMT_FLOAT64,

	FMT_STR_FIXED,
	FMT_STR8,
	FMT_STR16,
	FMT_STR32,
	FMT_STR64,
	FMT_STR_ZERO,

	FMT_PADDING,
} fmt_type_t;

typedef enum {
	FMT_OK,
	FMT_BAD_ARGS,
	FMT_INCOMPLETE_OP,
	FMT_BAD_OP_ARG,
	FMT_BAD_OP,
} fmt_code_t;

typedef struct {
	fmt_type_t type;
	size_t size, align;
} fmt_segment_t;

typedef struct {
	bool little_endian;
	size_t max_align;
	size_t segments_n;
	fmt_segment_t segments[];
} fmt_t;

static int fmt_parse_width(size_t *i, const char *raw, size_t raw_size) {
	if (*i < raw_size) {
		switch (raw[(*i)++]) {
			case '1': return 1;
			case '2': return 2;
			case '4': return 4;
			case '8': return 8;
			default:
				(*i)--;
				return 8;
		}
	}
	else return 8;
}

static fmt_code_t fmt_parse_fmt(lua_State *ctx, const char *raw, size_t raw_size) {
	if (raw == NULL || *raw == 0) return FMT_BAD_ARGS;
	if (raw_size == -1) raw_size = strlen(raw);

	fmt_segment_t segments[raw_size];
	size_t segments_n = 0;
	bool little_endian;
	bool max_align;

	size_t i = 0;
	bool curr_padding = false;

	while (true) {
		if (i >= raw_size) break;
		fmt_segment_t segment;

		switch (raw[i++]) {
			case '<': little_endian = true; continue;
			case '>':
			case '=': little_endian = false; continue;
			case '!':
				if (i < raw_size && (raw[i] < '0' || raw[i] > '9')) {
					max_align = raw[i] - '0';
					i++;
				}
				else max_align = 1;

				continue;

			case 'b': segment = (fmt_segment_t){ .type = FMT_INT8, .align = 1 }; break;
			case 'B': segment = (fmt_segment_t){ .type = FMT_UINT8, .align = 1 }; break;
			case 'h': segment = (fmt_segment_t){ .type = FMT_INT16, .align = 2 }; break;
			case 'H': segment = (fmt_segment_t){ .type = FMT_UINT16, .align = 2 }; break;
			case 'j': segment = (fmt_segment_t){ .type = FMT_INT32, .align = 4 }; break;
			case 'J': segment = (fmt_segment_t){ .type = FMT_UINT32, .align = 4 }; break;
			case 'l': segment = (fmt_segment_t){ .type = FMT_INT64, .align = 8 }; break;
			case 'L':
			case 'T': segment = (fmt_segment_t){ .type = FMT_UINT64, .align = 8 }; break;

			case 'f': segment = (fmt_segment_t){ .type = FMT_FLOAT32, .align = 4 }; break;
			case 'd':
			case 'n': segment = (fmt_segment_t){ .type = FMT_FLOAT64, .align = 8 }; break;

			case 'i':
				switch (fmt_parse_width(&i, raw, raw_size)) {
					case 1: segment = (fmt_segment_t){ .type = FMT_INT8, .align = 1 }; break;
					case 2: segment = (fmt_segment_t){ .type = FMT_INT16, .align = 2 }; break;
					case 4: segment = (fmt_segment_t){ .type = FMT_INT32, .align = 4 }; break;
					case 8: segment = (fmt_segment_t){ .type = FMT_INT64, .align = 8 }; break;
				}
				break;
			case 'I':
				switch (fmt_parse_width(&i, raw, raw_size)) {
					case 1: segment = (fmt_segment_t){ .type = FMT_UINT8, .align = 1 }; break;
					case 2: segment = (fmt_segment_t){ .type = FMT_UINT16, .align = 2 }; break;
					case 4: segment = (fmt_segment_t){ .type = FMT_UINT32, .align = 4 }; break;
					case 8: segment = (fmt_segment_t){ .type = FMT_UINT64, .align = 8 }; break;
				}
				break;

			case 'z': segment = (fmt_segment_t){ .type = FMT_STR_ZERO, .align = 1 }; break;
			case 'c':
				bool has_size;
				size_t str_size;

				while (i >= raw_size && raw[i] >= '0' && raw[i] <= '9') {
					str_size *= 10;
					str_size += raw[i] - '0';
					has_size = true;
					i++;
				}

				if (!has_size) return FMT_INCOMPLETE_OP;

				segment = (fmt_segment_t){ .type = FMT_STR_FIXED, .size = str_size, .align = 1 };
				break;
			case 's':
				switch (fmt_parse_width(&i, raw, raw_size)) {
					case 1: segment = (fmt_segment_t){ .type = FMT_STR8, .align = 1 }; break;
					case 2: segment = (fmt_segment_t){ .type = FMT_STR16, .align = 2 }; break;
					case 4: segment = (fmt_segment_t){ .type = FMT_STR32, .align = 4 }; break;
					case 8: segment = (fmt_segment_t){ .type = FMT_STR64, .align = 8 }; break;
				}
				break;

			case 'x': segment = (fmt_segment_t){ .type = FMT_PADDING, .size = 1, .align = 1 }; break;
			case 'X':
				curr_padding = true;
				continue;
			case ' ':
				break;

			default:
				return FMT_BAD_OP;
		}

		if (curr_padding) {
			// TODO: is this correct?
			switch (segment.type) {
				case FMT_INT8:
				case FMT_UINT8:
				case FMT_STR8:
					segment = (fmt_segment_t){ .type = FMT_PADDING, .size = 1, .align = 1 };
					break;
				case FMT_INT16:
				case FMT_UINT16:
				case FMT_STR16:
					segment = (fmt_segment_t){ .type = FMT_PADDING, .size = 2, .align = 2 };
					break;
				case FMT_INT32:
				case FMT_UINT32:
				case FMT_FLOAT32:
				case FMT_STR32:
					segment = (fmt_segment_t){ .type = FMT_PADDING, .size = 4, .align = 4 };
					break;
				case FMT_INT64:
				case FMT_UINT64:
				case FMT_FLOAT64:
				case FMT_STR64:
					segment = (fmt_segment_t){ .type = FMT_PADDING, .size = 8, .align = 8 };
					break;
				case FMT_STR_FIXED:
					segment = (fmt_segment_t){ .type = FMT_PADDING, .size = segment.size, .align = segment.size };
					break;
				default:
					return FMT_BAD_OP_ARG;
			}
		}

		segments[segments_n++] = segment;
		continue;
	}

	if (curr_padding) return FMT_INCOMPLETE_OP;

	for (size_t i = 0; i < segments_n; i++) {
		// TODO: this might not be correct...
		if (segments[i].align > max_align) segments[i].align = 8;
		if (segments[i].align > max_align) segments[i].align = 4;
		if (segments[i].align > max_align) segments[i].align = 2;
		if (segments[i].align > max_align) segments[i].align = 1;
	}

	fmt_t *res = lua_newuserdata(ctx, sizeof *res + sizeof *segments * segments_n);
	luaL_getmetatable(ctx, FMT_UDATA_NAME);
	lua_setmetatable(ctx, -2);

	res->little_endian = little_endian;
	res->max_align = max_align;
	res->segments_n = segments_n;
	memcpy(res->segments, segments, sizeof *segments * segments_n);

	return FMT_OK;
}


typedef struct {
	char *arr;
	size_t cap, n;
} write_buff_t;

static void write_buff_append(write_buff_t *buff, const char *data, size_t size) {
	size_t new_cap = buff->cap;

	while (new_cap < buff->n + size) {
		if (new_cap == 0) new_cap = 16;
		else new_cap *= 2;
	}

	if (new_cap != buff->cap) {
		if (buff->cap == 0) {
			buff->arr = malloc(new_cap);
		}
		else {
			buff->arr = realloc(buff->arr, new_cap);
		}
		buff->cap = new_cap;
	}

	if (data == NULL) {
		memset(buff->arr + buff->n, 0, size);
	}
	else {
		memcpy(buff->arr + buff->n, data, size);
	}

	buff->n += size;
}
static void write_buff_fit(write_buff_t *buff) {
	if (buff->arr == NULL) return;

	if (buff->n == 0) {
		free(buff->arr);
		buff->cap = 0;
	}
	else {
		buff->cap = buff->n;
		buff->arr = realloc(buff->arr, buff->n);
	}
}


static bool fmt_read_uint8(const uint8_t *raw, size_t *i, size_t size, uint8_t *res) {
	if ((*i) + 1 > size || *i < 0) return false;

	*res = raw[(*i)++];

	return true;
}
static bool fmt_read_int8(const uint8_t *raw, size_t *i, size_t size, int8_t *res) {
	return fmt_read_uint8(raw, i, size, (uint8_t*)res);
}

static bool fmt_read_uint16(const uint8_t *raw, size_t *i, size_t size, uint16_t *res, bool little_endian) {
	if ((*i) + 2 > size || *i < 0) return false;

	uint16_t a = raw[(*i)++];
	uint16_t b = raw[(*i)++];

	if (little_endian) *res = a | b << 8;
	else *res = a << 8 | b;

	return true;
}
static bool fmt_read_int16(const uint8_t *raw, size_t *i, size_t size, int16_t *res, bool little_endian) {
	return fmt_read_uint16(raw, i, size, (uint16_t*)res, little_endian);
}

static bool fmt_read_uint32(const uint8_t *raw, size_t *i, size_t size, uint32_t *res, bool little_endian) {
	if ((*i) + 4 > size || *i < 0) return false;

	uint8_t a = raw[(*i)++];
	uint8_t b = raw[(*i)++];
	uint8_t c = raw[(*i)++];
	uint8_t d = raw[(*i)++];

	if (little_endian) *res = a | b << 8 | c << 16 | d << 24;
	else *res = a << 24 | b << 16 | c << 8 | d;

	return true;
}
static bool fmt_read_int32(const uint8_t *raw, size_t *i, size_t size, int32_t *res, bool little_endian) {
	return fmt_read_uint32(raw, i, size, (uint32_t*)res, little_endian);
}

static bool fmt_read_uint64(const uint8_t *raw, size_t *i, size_t size, uint64_t *res, bool little_endian) {
	if ((*i) + 8 > size || *i < 0) return false;

	uint64_t a = raw[(*i)++];
	uint64_t b = raw[(*i)++];
	uint64_t c = raw[(*i)++];
	uint64_t d = raw[(*i)++];
	uint64_t e = raw[(*i)++];
	uint64_t f = raw[(*i)++];
	uint64_t g = raw[(*i)++];
	uint64_t h = raw[(*i)++];

	if (little_endian) *res = a | b << 8 | c << 16 | d << 24 | e << 32 | f << 40 | g << 48 | h << 56;
	else *res = a << 56 | b << 48 | c << 40 | d << 32 | e << 24 | f << 16 | g << 8 | h;

	return true;
}
static bool fmt_read_int64(const uint8_t *raw, size_t *i, size_t size, int64_t *res, bool little_endian) {
	return fmt_read_uint64(raw, i, size, (uint64_t*)res, little_endian);
}

static bool fmt_read_float32(const uint8_t *raw, size_t *i, size_t size, float *res, bool little_endian) {
	if ((*i) + 4 > size || *i < 0) return false;

	uint8_t a = raw[(*i)++];
	uint8_t b = raw[(*i)++];
	uint8_t c = raw[(*i)++];
	uint8_t d = raw[(*i)++];

	// TODO: is this portable enough?
	if (little_endian) *res = *(float*)(uint8_t[]) { a, b, c, d };
	else *res = *(float*)(uint8_t[]) { d, c, b, a };

	return true;
}
static bool fmt_read_float64(const uint8_t *raw, size_t *i, size_t size, double *res, bool little_endian) {
	if ((*i) + 8 > size || *i < 0) return false;

	uint8_t a = raw[(*i)++];
	uint8_t b = raw[(*i)++];
	uint8_t c = raw[(*i)++];
	uint8_t d = raw[(*i)++];
	uint8_t e = raw[(*i)++];
	uint8_t f = raw[(*i)++];
	uint8_t g = raw[(*i)++];
	uint8_t h = raw[(*i)++];

	// TODO: is this portable enough?
	if (little_endian) *res = *(float*)(uint8_t[]) { a, b, c, d, e, f, g, h };
	else *res = *(float*)(uint8_t[]) { h, g, f, e, d, c, b, a };

	return true;
}

static bool fmt_read_string(lua_State *ctx, fmt_segment_t segment, const uint8_t *raw, size_t *i, size_t size, bool little_endian) {
	uint64_t len;

	switch (segment.type) {
		case FMT_STR8: {
			uint8_t len8;
			if (!fmt_read_uint8(raw, i, size, &len8)) return false;
			break;
		}
		case FMT_STR16: {
			uint16_t len16;
			if (!fmt_read_uint16(raw, i, size, &len16, little_endian)) return false;
			len = len16;
			break;
		}
		case FMT_STR32: {
			uint32_t len32;
			if (!fmt_read_uint32(raw, i, size, &len32, little_endian)) return false;
			len = len32;
			break;
		}
		case FMT_STR64:
			if (!fmt_read_uint64(raw, i, size, &len, little_endian)) return false;
			break;
		case FMT_STR_FIXED:
			len = segment.size;
			break;
		case FMT_STR_ZERO:
			len = strnlen((const char*)(raw + *i), size - *i);
			if (len >= size - *i) return false;
			break;
		default:
			return false;
	}

	fprintf(stderr, "%lu %lu", len, *i);
	if ((*i) + len > size) return false;
	if (*i < 0) return false;

	char data[len];
	memcpy(data, raw + (*i), len);

	lua_pushlstring(ctx, data, len);
	return true;
}


static void fmt_write_uint8(write_buff_t *buff, uint8_t val) {
	write_buff_append(buff, (char[]){ val }, 1);
}
static void fmt_write_int8(write_buff_t *buff, int8_t val) {
	return fmt_write_uint8(buff, val);
}

static void fmt_write_uint16(write_buff_t *buff, uint16_t val, bool little_endian) {
	uint8_t a = val & 0xFF;
	uint8_t b = val >> 8 & 0xFF;

	if (little_endian) write_buff_append(buff, (char[]){ a, b }, 2);
	else write_buff_append(buff, (char[]){ b, a }, 2);
}
static void fmt_write_int16(write_buff_t *buff, uint16_t val, bool little_endian) {
	fmt_write_uint16(buff, val, little_endian);
}

static void fmt_write_uint32(write_buff_t *buff, uint32_t val, bool little_endian) {
	uint8_t a = val & 0xFF;
	uint8_t b = val >> 8 & 0xFF;
	uint8_t c = val >> 16 & 0xFF;
	uint8_t d = val >> 24 & 0xFF;

	if (little_endian) write_buff_append(buff, (char[]){ a, b, c, d }, 4);
	else write_buff_append(buff, (char[]){ d, c, b, a }, 4);
}
static void fmt_write_int32(write_buff_t *buff, uint32_t val, bool little_endian) {
	fmt_write_uint32(buff, val, little_endian);
}

static void fmt_write_uint64(write_buff_t *buff, uint64_t val, bool little_endian) {
	uint8_t a = val & 0xFF;
	uint8_t b = val >> 8 & 0xFF;
	uint8_t c = val >> 16 & 0xFF;
	uint8_t d = val >> 24 & 0xFF;
	uint8_t e = val >> 32 & 0xFF;
	uint8_t f = val >> 40 & 0xFF;
	uint8_t g = val >> 48 & 0xFF;
	uint8_t h = val >> 56 & 0xFF;

	if (little_endian) write_buff_append(buff, (char[]){ a, b, c, d, e, f, g, h }, 8);
	else write_buff_append(buff, (char[]){ h, g, f, e, d, c, b, a }, 8);
}
static void fmt_write_int64(write_buff_t *buff, uint64_t val, bool little_endian) {
	fmt_write_uint64(buff, val, little_endian);
}

static void fmt_write_float32(write_buff_t *buff, float val, bool little_endian) {
	uint32_t ival = *(uint32_t*)&val;

	uint8_t a = ival & 0xFF;
	uint8_t b = ival >> 8 & 0xFF;
	uint8_t c = ival >> 16 & 0xFF;
	uint8_t d = ival >> 24 & 0xFF;

	if (little_endian) write_buff_append(buff, (char[]){ a, b, c, d }, 4);
	else write_buff_append(buff, (char[]){ d, c, b, a }, 4);
}
static void fmt_write_float64(write_buff_t *buff, double val, bool little_endian) {
	uint64_t ival = *(uint64_t*)&val;

	uint8_t a = ival & 0xFF;
	uint8_t b = ival >> 8 & 0xFF;
	uint8_t c = ival >> 16 & 0xFF;
	uint8_t d = ival >> 24 & 0xFF;
	uint8_t e = ival >> 32 & 0xFF;
	uint8_t f = ival >> 40 & 0xFF;
	uint8_t g = ival >> 48 & 0xFF;
	uint8_t h = ival >> 56 & 0xFF;

	if (little_endian) write_buff_append(buff, (char[]){ a, b, c, d, e, f, g, h }, 8);
	else write_buff_append(buff, (char[]){ h, g, f, e, d, c, b, a }, 8);
}

static bool fmt_write_string(write_buff_t *buff, fmt_segment_t segment, const char *str, size_t len, bool little_endian) {
	switch (segment.type) {
		case FMT_STR8:
			if (len > 256) return false;
			fmt_write_uint8(buff, (uint8_t)len);
			write_buff_append(buff, str, len);
			return true;
		case FMT_STR16:
			if (len > 0x10000) return false;
			fmt_write_uint16(buff, (uint16_t)len, little_endian);
			write_buff_append(buff, str, len);
			return true;
		case FMT_STR32:
			if (len > 0x100000000) return false;
			fmt_write_uint32(buff, (uint32_t)len, little_endian);
			write_buff_append(buff, str, len);
			return true;
		case FMT_STR64:
			fmt_write_uint64(buff, len, little_endian);
			write_buff_append(buff, str, len);
			return true;
		case FMT_STR_FIXED:
			if (len > segment.size) return false;
			write_buff_append(buff, str, len);
			write_buff_append(buff, NULL, segment.size - len);
			return true;
		case FMT_STR_ZERO:
			if (strlen(str) != len) return false;
			write_buff_append(buff, str, len);
			write_buff_append(buff, (char[]) { 0x00 }, 1);
			return true;
		default:
			return false;
	}
}


static int lib_fmt_pack(lua_State *ctx) {
	fmt_t *fmt = luaL_checkudata(ctx, 1, FMT_UDATA_NAME);

	size_t arg_i = 2;
	write_buff_t buff = { .arr = NULL, .n = 0, .cap = 0 };

	for (size_t i = 0; i < fmt->segments_n; i++) {
		fmt_segment_t segment = fmt->segments[i];

		size_t n_aligned = -((-buff.n / segment.align) * segment.align);
		size_t align_padding = n_aligned - buff.n;
		write_buff_append(&buff, NULL, align_padding);

		switch (segment.type) {
			case FMT_INT8:
				fmt_write_int8(&buff, luaL_checkinteger(ctx, arg_i++));
				break;
			case FMT_UINT8:
				fmt_write_uint8(&buff, luaL_checkinteger(ctx, arg_i++));
				break;
			case FMT_INT16:
				fmt_write_int16(&buff, luaL_checkinteger(ctx, arg_i++), fmt->little_endian);
				break;
			case FMT_UINT16:
				fmt_write_uint16(&buff, luaL_checkinteger(ctx, arg_i++), fmt->little_endian);
				break;
			case FMT_INT32:
				fmt_write_int32(&buff, luaL_checkinteger(ctx, arg_i++), fmt->little_endian);
				break;
			case FMT_UINT32:
				fmt_write_uint32(&buff, luaL_checkinteger(ctx, arg_i++), fmt->little_endian);
				break;
			case FMT_INT64:
				fmt_write_int64(&buff, luaL_checkinteger(ctx, arg_i++), fmt->little_endian);
				break;
			case FMT_UINT64:
				fmt_write_uint64(&buff, luaL_checkinteger(ctx, arg_i++), fmt->little_endian);
				break;

			case FMT_FLOAT32:
				fmt_write_float32(&buff, (float)luaL_checknumber(ctx, arg_i++), fmt->little_endian);
				break;
			case FMT_FLOAT64:
				fmt_write_float64(&buff, (double)luaL_checknumber(ctx, arg_i++), fmt->little_endian);
				break;

			case FMT_STR_FIXED:
			case FMT_STR8:
			case FMT_STR16:
			case FMT_STR32:
			case FMT_STR64:
			case FMT_STR_ZERO: {
				size_t size;
				const char *str = luaL_checklstring(ctx, arg_i++, &size);
				if (!fmt_write_string(&buff, segment, str, size, fmt->little_endian)) {
					luaL_error(ctx, "invalid string at %d", arg_i);
				}
				break;
			}

			case FMT_PADDING:
				// TODO: might need to remove this later...
				write_buff_append(&buff, NULL, segment.size);
		}
	}

	write_buff_fit(&buff);
	lua_pushlstring(ctx, buff.arr, buff.n);
	free(buff.arr);

	return 1;
}

static int lib_fmt_unpack(lua_State *ctx) {
	fmt_t *fmt = luaL_checkudata(ctx, 1, FMT_UDATA_NAME);

	size_t raw_size;
	const uint8_t *raw = (const uint8_t*)luaL_checklstring(ctx, 2, &raw_size);

	size_t read_i = 0;
	size_t res_n = 0;
	if (lua_isinteger(ctx, 3)) {
		read_i = lua_tointeger(ctx, 3) - 1;
	}

	write_buff_t buff = { .arr = NULL, .n = 0, .cap = 0 };

	for (size_t i = 0; i < fmt->segments_n; i++) {
		fmt_segment_t segment = fmt->segments[i];

		size_t n_aligned = -((-buff.n / segment.align) * segment.align);
		size_t align_padding = n_aligned - buff.n;
		read_i += align_padding;

		switch (segment.type) {
			case FMT_INT8: {
				int8_t res;
				if (!fmt_read_int8(raw, &read_i, raw_size, &res)) luaL_error(ctx, "couldn't read int8");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_UINT8: {
				uint8_t res;
				if (!fmt_read_uint8(raw, &read_i, raw_size, &res)) luaL_error(ctx, "couldn't read uint8");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_INT16: {
				int16_t res;
				if (!fmt_read_int16(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read int16");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_UINT16: {
				uint16_t res;
				if (!fmt_read_uint16(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read uint16");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_INT32: {
				int32_t res;
				if (!fmt_read_int32(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read int32");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_UINT32: {
				uint32_t res;
				if (!fmt_read_uint32(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read uint32");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_INT64: {
				int64_t res;
				if (!fmt_read_int64(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read int64");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_UINT64: {
				uint64_t res;
				if (!fmt_read_uint64(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read uint64");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}

			case FMT_FLOAT32: {
				float res;
				if (!fmt_read_float32(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read float32");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}
			case FMT_FLOAT64: {
				double res;
				if (!fmt_read_float64(raw, &read_i, raw_size, &res, fmt->little_endian)) luaL_error(ctx, "couldn't read float64");
				lua_pushinteger(ctx, res);
				res_n++;
				break;
			}

			case FMT_STR_FIXED:
			case FMT_STR8:
			case FMT_STR16:
			case FMT_STR32:
			case FMT_STR64:
			case FMT_STR_ZERO: {
				if (!fmt_read_string(ctx, segment, raw, &read_i, raw_size, fmt->little_endian)) luaL_error(ctx, "couldn't read string");
				res_n++;
				break;
			}

			case FMT_PADDING:
				read_i += segment.size;
				break;
		}
	}

	lua_pushinteger(ctx, read_i + 1);
	return res_n + 1;
}


static int lib_fmt_new(lua_State *ctx) {
	size_t raw_size;
	const char *raw = luaL_checklstring(ctx, 1, &raw_size);
	fmt_code_t code = fmt_parse_fmt(ctx, raw, raw_size);

	if (code != FMT_OK) {
		switch (code) {
			case FMT_BAD_ARGS: return luaL_error(ctx, "illegal C arguments");
			case FMT_INCOMPLETE_OP: return luaL_error(ctx, "incomplete operand in format string");
			case FMT_BAD_OP_ARG: return luaL_error(ctx, "bad operand argument in format string");
			case FMT_BAD_OP: return luaL_error(ctx, "bad operand in format string");
			default: return luaL_error(ctx, "unknown error while parsing format string");
		}
	}

	return 1;
}


static void fmt_init_meta(lua_State *ctx) {
	luaL_newmetatable(ctx, FMT_UDATA_NAME);

	luaL_newlib(ctx, ((luaL_Reg[]) {
		{ "pack", lib_fmt_pack },
		{ "unpack", lib_fmt_unpack },
		{ NULL, NULL }
	}));
	lua_setfield(ctx, -2, "__index");

	lua_pushboolean(ctx, false);
	lua_setfield(ctx, -2, "__meta");

	lua_pop(ctx, 1);
}

int fmt_open_lib(lua_State *ctx) {
	fmt_init_meta(ctx);

	luaL_newlib(ctx, ((luaL_Reg[]) {
		{ "new", lib_fmt_new },
		{ "pack", lib_fmt_pack },
		{ "unpack", lib_fmt_unpack },
		{ NULL, NULL },
	}));

	return 1;
}