init

1 files changed, 123 insertions, 0 deletions

diff --git a/unpack.c b/unpack.c
new file mode 100644
index 0000000..2617e9a
--- /dev/null
+++ b/unpack.c
@@ -0,0 +1,123 @@
+#include <ctype.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <limits.h>
+
+#include <stdio.h>
+
+#include "common.h"
+#include "pack.h"
+
+typedef enum pack_status unpacker(void *buf, size_t size, va_list ap);
+
+enum endian { BIG, LITTLE };
+
+uintmax_t read_val(unsigned char *buf, size_t size, enum endian e)
+{
+	unsigned long long val = 0;
+
+	for (size_t i = 0; i < size; i++)
+		val |= (buf[i] & 0xff) << (e == LITTLE ? i : size - i - 1) * 8;
+
+	return val;
+}
+#define X(M) \
+	M(b, signed   char     ) \
+	M(B, unsigned char     ) \
+	M(h,          short    ) \
+	M(H, unsigned short    ) \
+	M(i,          int      ) \
+	M(I, unsigned          ) \
+	M(l,          long     ) \
+	M(L, unsigned long     ) \
+	M(q,          long long) \
+	M(Q, unsigned long long)
+
+enum pack_status unpack(void *buf_, size_t size, const char *fmt, ...)
+{
+	enum endian endianness = BIG;
+	unsigned char *buf = buf_;
+	size_t offset = 0;
+	va_list ap;
+
+	va_start(ap, fmt);
+
+	for (int i = 0; fmt[i] != '\0'; i++) {
+		bool sign = islower(fmt[i]);
+		size_t s;
+		union {
+			signed   char      *b;
+			unsigned char      *B;
+			         short     *h;
+			unsigned short     *H;
+			         int       *i;
+			unsigned int       *I;
+			         long      *l;
+			unsigned long      *L;
+			         long long *q;
+			unsigned long long *Q;
+		} arg;
+		/*void *arg;*/
+		union { uintmax_t u; intmax_t s; } val;
+		switch (fmt[i]) {
+		case '>': endianness = BIG; continue;
+		case '<': endianness = LITTLE; continue;
+		case 'b': arg.b = va_arg(ap, signed   char      *);
+		case 'B': arg.B = va_arg(ap, unsigned char      *);
+		case 'h': arg.h = va_arg(ap,          short     *);
+		case 'H': arg.H = va_arg(ap, unsigned short     *);
+		case 'i': arg.i = va_arg(ap,          int       *);
+		case 'I': arg.I = va_arg(ap, unsigned           *);
+		case 'l': arg.l = va_arg(ap,          long      *);
+		case 'L': arg.L = va_arg(ap, unsigned long      *);
+		case 'q': arg.q = va_arg(ap,          long long *);
+		case 'Q': arg.Q = va_arg(ap, unsigned long long *);
+		case 'x': break;
+		return PACK_FMTINVAL;
+		}
+
+		s = getsize(fmt[i]);
+		if (s == (size_t)-1) return PACK_FMTINVAL;
+
+		if (size - offset < s) return PACK_TOOSMALL;
+
+		if (fmt[i] == 'x') goto skip;
+
+		val.u = read_val(buf, s, endianness);
+
+		fprintf(stderr, "%zu, %llu\n", s, val.u);
+
+		if (sign) {
+			intmax_t vals;
+			if (!(val.u & (1llu << (s * 8 - 1)))) {
+				vals = val.u;
+			} else {
+				uintmax_t offt = UINTMAX_MAX >> (sizeof offt * CHAR_BIT - s * 8);
+				vals = val.u - offt - 1;
+			}
+			val.s = vals;
+			fprintf(stderr, "signed %lld\n", val.s);
+		}
+
+		switch (fmt[i]) {
+#define D(t, f) fprintf(stderr, "(%p) "#t " = %" #f "\n", (void *)arg.t, *arg.t)
+		case 'b': *arg.b = val.s; D(b, d); break;
+		case 'B': *arg.B = val.u; D(B, u); break;
+		case 'h': *arg.h = val.s; D(h, d); break;
+		case 'H': *arg.H = val.u; D(H, u); break;
+		case 'i': *arg.i = val.s; D(i, d); break;
+		case 'I': *arg.I = val.u; D(I, u); break;
+		case 'l': *arg.l = val.s; D(l, ld); break;
+		case 'L': *arg.L = val.u; D(L, lu); break;
+		case 'q': *arg.q = val.s; D(q, lld); break;
+		case 'Q': *arg.Q = val.u; D(Q, llu); break;
+		}
+skip:
+		offset += s;
+	}
+
+	va_end(ap);
+
+	return PACK_OK;
+}