archival/libarchive/open_transformer.c

/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"
#include "bb_archive.h"

#define ZIPPED (ENABLE_FEATURE_SEAMLESS_LZMA \
	|| ENABLE_FEATURE_SEAMLESS_BZ2 \
	|| ENABLE_FEATURE_SEAMLESS_GZ \
	/* || ENABLE_FEATURE_SEAMLESS_Z */ \
)

#if ZIPPED
# include "bb_archive.h"
#endif

/* transformer(), more than meets the eye */
/*
 * On MMU machine, the transform_prog is removed by macro magic
 * in include/archive.h. On NOMMU, transformer is removed.
 */
void FAST_FUNC open_transformer(int fd,
	IF_DESKTOP(long long) int FAST_FUNC (*transformer)(int src_fd, int dst_fd),
	const char *transform_prog)
{
	struct fd_pair fd_pipe;
	int pid;

	xpiped_pair(fd_pipe);
	pid = BB_MMU ? xfork() : xvfork();
	if (pid == 0) {
		/* Child */
		close(fd_pipe.rd); /* we don't want to read from the parent */
		// FIXME: error check?
#if BB_MMU
		transformer(fd, fd_pipe.wr);
		if (ENABLE_FEATURE_CLEAN_UP) {
			close(fd_pipe.wr); /* send EOF */
			close(fd);
		}
		/* must be _exit! bug was actually seen here */
		_exit(EXIT_SUCCESS);
#else
		{
			char *argv[4];
			xmove_fd(fd, 0);
			xmove_fd(fd_pipe.wr, 1);
			argv[0] = (char*)transform_prog;
			argv[1] = (char*)"-cf";
			argv[2] = (char*)"-";
			argv[3] = NULL;
			BB_EXECVP(transform_prog, argv);
			bb_perror_msg_and_die("can't execute '%s'", transform_prog);
		}
#endif
		/* notreached */
	}

	/* parent process */
	close(fd_pipe.wr); /* don't want to write to the child */
	xmove_fd(fd_pipe.rd, fd);
}


/* Used by e.g. rpm which gives us a fd without filename,
 * thus we can't guess the format from filename's extension.
 */
#if ZIPPED
void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
{
	const int fail_if_not_detected = 1;
	union {
		uint8_t b[4];
		uint16_t b16[2];
		uint32_t b32[1];
	} magic;
	int offset = -2;
# if BB_MMU
	IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
	enum { xformer_prog = 0 };
# else
	enum { xformer = 0 };
	const char *xformer_prog;
# endif

	/* .gz and .bz2 both have 2-byte signature, and their
	 * unpack_XXX_stream wants this header skipped. */
	xread(fd, magic.b16, sizeof(magic.b16[0]));
	if (ENABLE_FEATURE_SEAMLESS_GZ
	 && magic.b16[0] == GZIP_MAGIC
	) {
# if BB_MMU
		xformer = unpack_gz_stream;
# else
		xformer_prog = "gunzip";
# endif
		goto found_magic;
	}
	if (ENABLE_FEATURE_SEAMLESS_BZ2
	 && magic.b16[0] == BZIP2_MAGIC
	) {
# if BB_MMU
		xformer = unpack_bz2_stream;
# else
		xformer_prog = "bunzip2";
# endif
		goto found_magic;
	}
	if (ENABLE_FEATURE_SEAMLESS_XZ
	 && magic.b16[0] == XZ_MAGIC1
	) {
		offset = -6;
		xread(fd, magic.b32, sizeof(magic.b32[0]));
		if (magic.b32[0] == XZ_MAGIC2) {
# if BB_MMU
			xformer = unpack_xz_stream;
			/* unpack_xz_stream wants fd at position 6, no need to seek */
			//xlseek(fd, offset, SEEK_CUR);
# else
			xformer_prog = "unxz";
# endif
			goto found_magic;
		}
	}

	/* No known magic seen */
	if (fail_if_not_detected)
		bb_error_msg_and_die("no gzip"
			IF_FEATURE_SEAMLESS_BZ2("/bzip2")
			IF_FEATURE_SEAMLESS_XZ("/xz")
			" magic");
	xlseek(fd, offset, SEEK_CUR);
	return;

 found_magic:
# if !BB_MMU
	/* NOMMU version of open_transformer execs
	 * an external unzipper that wants
	 * file position at the start of the file */
	xlseek(fd, offset, SEEK_CUR);
# endif
	open_transformer(fd, xformer, xformer_prog);
}
#endif /* ZIPPED */

int FAST_FUNC open_zipped(const char *fname)
{
#if !ZIPPED
	return open(fname, O_RDONLY);
#else
	char *sfx;
	int fd;

	fd = open(fname, O_RDONLY);
	if (fd < 0)
		return fd;

	sfx = strrchr(fname, '.');
	if (sfx) {
		sfx++;
		if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, "lzma") == 0)
			/* .lzma has no header/signature, just trust it */
			open_transformer(fd, unpack_lzma_stream, "unlzma");
		else
		if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, "gz") == 0)
		 || (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, "bz2") == 0)
		 || (ENABLE_FEATURE_SEAMLESS_XZ && strcmp(sfx, "xz") == 0)
		) {
			setup_unzip_on_fd(fd /*, fail_if_not_detected: 1*/);
		}
	}

	return fd;
#endif
}

void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_p)
{
	int fd;
	char *image;

	fd = open_zipped(fname);
	if (fd < 0)
		return NULL;

	image = xmalloc_read(fd, maxsz_p);
	if (!image)
		bb_perror_msg("read error from '%s'", fname);
	close(fd);

	return image;
}