simgconvert.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

/* read 32bit little endian integer */
int read_leint (FILE *in, uint32_t *outint)
{
	unsigned char bytes[4];
	if (fread(bytes, 4, 1, in) != 1)
		return 1;
	*outint = (bytes[3] << 24) |
		(bytes[2] << 16) |
		(bytes[1] << 8) |
		bytes[0];
	return 0;
}

void hexdump (const char *msg, const unsigned char *data, size_t len)
{
	int i;
	fprintf(stderr, "%s: ", msg);
	for (i = 0; i < len; i ++) {
		fprintf(stderr, "%02x", data[i]);
		fprintf(stderr, "%c", i == len - 1 ? '\n' : ' ');
	}
}

int copyField (FILE *in, FILE *out)
{
	uint32_t n1, size;
	unsigned char buffer[8192];

	if (read_leint(in, &n1) || read_leint(in, &size)) {
		fprintf(stderr, "Unexpected EOF\n");
		return 1;
	}
	fprintf(stderr, "copyField: %x %x\n", n1, size);

	size -= 12;
	while (size > 0) {
		size_t len = size < sizeof(buffer) ? size : sizeof(buffer);
		if (fread(buffer, len, 1, in) != 1) {
			fprintf(stderr, "Unexpected EOF\n");
			return 1;
		}
		fwrite(buffer, len, 1, out);
		size -= len;
	}

	return 0;
}

int writeZeros (FILE *in, FILE *out)
{
	uint32_t pages, n2;
	unsigned char buffer[4096] = {0};

	if (read_leint(in, &pages) || read_leint(in, &n2)) {
		fprintf(stderr, "Unexpected EOF\n");
		return 1;
	}
	fprintf(stderr, "writeZeros: %x %x\n", pages, n2);

	for (; pages > 0; pages --)
		fwrite(buffer, 4096, 1, out);

	return 0;
}

int convert (FILE *in, FILE *out)
{
	unsigned char buffer[4096];

	if (fread(buffer, 1, 28, in) != 28) {
		fprintf(stderr, "File too short\n");
		return 1;
	}
	hexdump("H28", buffer, 28);

	while (1) {
		uint32_t opcode;
		if (read_leint(in, &opcode)) {
			return 0;
		}
		switch (opcode) {
		case 0xCAC1:
			if (copyField(in, out))
				return 1;
			break;
		case 0xCAC3:
			if (writeZeros(in, out))
				return 1;
			break;
		default:
			fprintf(stderr, "Invalid header %x\n", opcode);
			return 1;
		}
	}
}

int main (void)
{
	return convert(stdin, stdout);
}