aboutsummaryrefslogtreecommitdiffstats
path: root/unpack.c
blob: 995eac83cdc4108cfd3005744c9677b82b1a2cf4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
/*
 * Copyright (C) 2020-2021  Tomasz Kramkowski <tk@the-tk.com>
 * SPDX-License-Identifier: MIT
 */
#include <ctype.h>
#include <errno.h>
#include <inttypes.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>

#include "common.h"
#include "ieee754b.h"
#include "pack.h"
#include "trace.h"

struct dest {
	enum pack_type type;
	union ptr {
		#define T(type, sign, c_type, va_type) sign c_type *type;
		ITYPE_MACROS
		#undef T
		float *f;
		double *d;
	} ptr;
	size_t count;
};

static uintmax_t read_val(const unsigned char *buf, size_t size, enum pack_endian e)
{
	uintmax_t val = 0;

	for (size_t i = 0; i < size; i++) {
		val |= (uintmax_t)(buf[i] & 0xff) << (e == PACK_ENDIAN_LITTLE ? i : size - i - 1) * 8;
	}

	return val;
}

static intmax_t minval(size_t s)
{
	switch (s) {
	case 1: return INTMAX_C(-128);
	case 2: return INTMAX_C(-32768);
	case 4: return INTMAX_C(-2147483648);
	default: return -INTMAX_C(9223372036854775807) - 1;
	}
}

static void read_fields(struct dest dest, const void *src_, enum pack_endian endianness)
{
	union {
		uintmax_t unsigned_;
		intmax_t signed_;
		float f;
		double d;
	} val;
	const unsigned char *src = src_;
	size_t s = getsize(dest.type);

	for (size_t i = 0; i < dest.count; i++) {
		val.unsigned_ =
			read_val(&src[s * i], s, endianness);
		tr_debug("val.u: %" PRIuMAX ", at: %" PRIuSIZE,
			 val.unsigned_, s * i);

		if (dest.type == PACK_TYPE_FLOAT) {
			float f = ieee754b32_deserialise(val.unsigned_);
			val.f = f;
			tr_debug("val.f: %f", val.f);
		} else if (dest.type == PACK_TYPE_DOUBLE) {
			double d = ieee754b64_deserialise(val.unsigned_);
			val.d = d;
			tr_debug("val.d: %f", val.d);
		} else if (islower((char)dest.type)) {
			intmax_t vals;
			if (!(val.unsigned_ & (UINTMAX_C(1) << (s * 8 - 1)))) {
				vals = val.unsigned_;
			} else {
				vals = minval(s);
				vals += val.unsigned_ ^ (UINTMAX_C(1) << (s * 8 - 1));
			}
			val.signed_ = vals;
			tr_debug("val.s: %" PRIdMAX, val.signed_);
		}

		switch (dest.type) {
		#define T(type, sign, c_type, va_type) \
			case (char)PACK_TYPE_##type: \
				dest.ptr.type[i] = val.sign##_; \
				break;
		ITYPE_MACROS
		#undef T
		case PACK_TYPE_FLOAT: dest.ptr.f[i] = val.f; break;
		case PACK_TYPE_DOUBLE: dest.ptr.d[i] = val.d; break;
		case PACK_TYPE_PADDING: break;
		case PACK_TYPE_COUNT: return;
		}
	}
}

enum pack_status unpack(const void *buf_, size_t size, const char *fmt, ...)
{
	enum pack_endian endianness = PACK_ENDIAN_BIG;
	const unsigned char *buf = buf_;
	enum pack_status ret = PACK_OK;
	size_t offset = 0;
	va_list ap;

	tr_call("unpack(%p, %" PRIuSIZE ", %s, ...)", (const void *)buf, size, fmt);

	va_start(ap, fmt);

	for (int i = 0; fmt[i] != '\0'; i++) {
		size_t s;
		struct dest dest = { .count = 1 };
		tr_debug("i: %d, fmt[i]: %c", i, fmt[i]);
		if (isdigit(fmt[i])) {
			unsigned long long c;
			char *end;

			errno = 0;
			c = strtoull(&fmt[i], &end, 10);
			if ((c == ULLONG_MAX && errno == ERANGE) || c > SIZE_MAX)
				SET_AND_GOTO(ret, PACK_FMTINVAL, stop);
			dest.count = c;
			i += end - &fmt[i];
		} else if (fmt[i] == PACK_TYPE_COUNT) {
			dest.count = va_arg(ap, size_t);
			i++;
		}
		tr_debug("dest.count: %" PRIuSIZE ", i: %d, fmt[i]: %c", dest.count, i, fmt[i]);
		switch (fmt[i]) {
		case '>': endianness = PACK_ENDIAN_BIG; continue;
		case '<': endianness = PACK_ENDIAN_LITTLE; continue;
		#define T(type, sign, c_type, va_type) \
			case (char)PACK_TYPE_##type: \
				dest.ptr.type = va_arg(ap, sign c_type *); \
				break;
		ITYPE_MACROS
		#undef T
		case PACK_TYPE_FLOAT: dest.ptr.f = va_arg(ap, float *); break;
		case PACK_TYPE_DOUBLE: dest.ptr.d = va_arg(ap, double *); break;
		case PACK_TYPE_PADDING: break;
		default: SET_AND_GOTO(ret, PACK_FMTINVAL, stop);
		}
		dest.type = fmt[i];

		s = getsize(dest.type);
		tr_debug("s: %" PRIuSIZE, s);
		if (s == (size_t)-1) SET_AND_GOTO(ret, PACK_FMTINVAL, stop);

		if (size - offset < s * dest.count)
			SET_AND_GOTO(ret, PACK_TOOSMALL, stop);

		if (dest.type != PACK_TYPE_PADDING)
			read_fields(dest, &buf[offset], endianness);

		offset += s * dest.count;
	}

stop:
	va_end(ap);

	return ret;
}

enum pack_status unpack_struct(const void *buf_, size_t size,
                               const struct pack_args *args, void *dest_)
{
	const unsigned char *buf = buf_;
	char *dest = dest_;
	size_t offset = 0;

	tr_call("unpack_struct(%p, %" PRIuSIZE ", %p, %p)", \
	        (const void *)buf, size, (const void *)args, (const void *)dest);

	tr_debug("args->endian: %s, args->fields: %p, args->num_fields: %" PRIuSIZE,
	         args->endian == PACK_ENDIAN_BIG ? "big" : "little",
	         (const void *)args->fields, args->num_fields);

	for (size_t i = 0; i < args->num_fields; i++) {
		#define FIELD (void *)&dest[f->offset]
		const struct pack_field *f = &args->fields[i];
		struct pack_field indirect;
		struct dest field;
		size_t s;

		if (f->type == PACK_TYPE_COUNT) {
			if (i + 1 >= args->num_fields) return PACK_FMTINVAL;
			indirect = args->fields[++i];
			indirect.count = *(size_t *)FIELD;
			f = &indirect;
		}

		s = getsize(f->type);
		if (s == (size_t)-1) return PACK_FMTINVAL;

		tr_debug("i: %" PRIuSIZE ", f->type: %c, f->count: %" PRIuSIZE ", "
		         "f->offset: %" PRIuSIZE ", s: %" PRIuSIZE,
		         i, (char)f->type, f->count, f->offset, s);

		field.type = f->type;
		switch (field.type) {
		#define T(type, sign, c_type, va_type) \
			case PACK_TYPE_##type: field.ptr.type = FIELD; break;
		ITYPE_MACROS
		#undef T
		case PACK_TYPE_FLOAT: field.ptr.f = FIELD; break;
		case PACK_TYPE_DOUBLE: field.ptr.d = FIELD; break;
		case PACK_TYPE_PADDING: break;
		default: return PACK_FMTINVAL;
		}
		field.count = f->count;

		if (size - offset < s * field.count) return PACK_TOOSMALL;

		if (f->type != PACK_TYPE_PADDING)
			read_fields(field, &buf[offset], args->endian);

		offset += s * field.count;
		#undef FIELD
	}

	return PACK_OK;
}