/* vi: set sw=4 ts=4: */
/*
 * Mini rpm2cpio implementation for busybox
 *
 * Copyright (C) 2001 by Laurence Anderson
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <errno.h>
#include <zlib.h>

#define RPM_MAGIC "\355\253\356\333"
#define RPM_HEADER_MAGIC "\216\255\350"
//#define RPM_LEAD_MAGIC 0xedabeedb
#define RPM_LEAD_MAGIC 0xdbeeabed
#define RPM_HEADER_MAGICnVER 0x8eade801
#define CHUNK 16

#define FTEXT    1
#define FHCRC    2
#define FEXTRA   4
#define FNAME    8
#define FCOMMENT 16

typedef struct rpm_lead {
    uint32_t magic;
    uint8_t major, minor;
    uint16_t type;
    uint16_t archnum;
    char name[66];
    uint16_t osnum;
    uint16_t signature_type;
    char reserved[16];
} __attribute__((packed)) rpm_lead_t;

typedef struct rpm_header {
	char magic[3]; /* 3 byte magic: 0x8e 0xad 0xe8 */
	uint8_t version; /* 1 byte version number */
	uint32_t reserved; /* 4 bytes reserved */
	uint32_t entries; /* Number of entries in header (4 bytes) */
	uint32_t size; /* Size of store (4 bytes) */
} __attribute__((packed)) rpm_header_t;

static __attribute__((always_inline)) inline uint32_t av_bswap32(uint32_t x)
{
    __asm__("bswap   %0" : "+r" (x));
    return x;
}

static ssize_t safe_read(int fd, void *buf, size_t count)
{
    ssize_t n;

    do {
        n = read(fd, buf, count);
    } while ((n < 0) && (errno == EINTR));

    return n;
}

static unsigned int skip_header(int rpm_fd)
{
	rpm_header_t header;
    unsigned int len;

	read(rpm_fd, &header, sizeof(rpm_header_t));
	if (strncmp((char *) &header.magic, RPM_HEADER_MAGIC, 3) != 0) {
		fprintf(stderr, "rpm2cpio: error: invalid RPM header magic.\n"); /* Invalid magic */
        return 0;
	}
	if (header.version != 1) {
		fprintf(stderr, "rpm2cpio: error: unsupported RPM header version!\n"); /* This program only supports v1 headers */
        return 0;
	}
	header.entries = av_bswap32(header.entries);
	header.size = av_bswap32(header.size);
    //len = 16 * av_bswap32(header.entries) + av_bswap32(header.size);
    len = 16 * header.entries + header.size;
	lseek (rpm_fd, len, SEEK_CUR); /* Seek past index entries, and past store. */
    return sizeof(header) + len;
}

static unsigned int skip_null_terminated_crap(int rpm_fd)
{
    char buf[1024], *end = buf;
    ssize_t offset, len = 0, rd;

    do {
        rd = safe_read(rpm_fd, buf, 1024);
        if(rd < 0) {
            fprintf(stderr, "error: read(): %s\n", strerror(errno));
            return 0;
        }
        end = memchr(buf, '\0', 1024);
        len += 1024;
    } while (!end && (rd > 0));

    offset = (size_t)(end - buf);
    len -= 1024;
    len += offset;
    lseek(rpm_fd, -(1024 - offset), SEEK_CUR);
    return len;
}

static unsigned int skip_gzip_header(int rpm_fd)
{
    unsigned int start, magic;
    unsigned char buf[2], flg;

    /* get flag byte */
    //read(rpm_fd, &magic, 4);
    //flg = (magic >> 24);
    read(rpm_fd, buf, 2);
    flg = buf[1];

    /* check id bytes */
    //magic &= 0xe0ffffff;
    //if (magic != 0x00088b1f) return Z_DATA_ERROR;

    /* check that reserved bits are zero */
    if (flg & 0xe0) return Z_DATA_ERROR;

    /* -- find start of compressed data -- */

    /* skip base header of 10 bytes */
    start = 10;
    lseek(rpm_fd, 6, SEEK_CUR);

    /* skip extra data if present */
    if (flg & FEXTRA) { unsigned int xlen; read(rpm_fd, &xlen, 2); xlen &= 0xffff; start += xlen + 2; lseek(rpm_fd, SEEK_CUR, xlen+2); }
    
    /* skip file name if present */
    if (flg & FNAME) { /*while (*start) ++start; ++start;*/ start += skip_null_terminated_crap(rpm_fd); }
    
    /* skip file comment if present */
    if (flg & FCOMMENT) { /*while (*start) ++start; ++start;*/ start += skip_null_terminated_crap(rpm_fd); }
    
    /* skip header crc if present */
    start += (flg & FHCRC);
    lseek(rpm_fd, (flg & FHCRC), SEEK_CUR);
    return start;
}

const char * const z_errmsg[10] = {
"Need DEFLATE Dictionary",/* Z_NEED_DICT       2  */
"Reached end of stream",  /* Z_STREAM_END      1  */
"Success",                /* Z_OK              0  */
"File error",             /* Z_ERRNO         (-1) */
"Stream error",           /* Z_STREAM_ERROR  (-2) */
"Data error",             /* Z_DATA_ERROR    (-3) */
"Insufficient Memory",    /* Z_MEM_ERROR     (-4) */
"Buffer error",           /* Z_BUF_ERROR     (-5) */
"Incompatible zlib version",/* Z_VERSION_ERROR (-6) */
""
};

static const char *zlib_errstr(int r)
{
    r = -r + 2;
    if (r < 9) {
        return z_errmsg[r];
    } else {
        return "Unknown zlib error, this should never happen.";
    }
}

/* Decompress from file source to file dest until stream ends or EOF.
   inf() returns Z_OK on success, Z_MEM_ERROR if memory could not be
   allocated for processing, Z_DATA_ERROR if the deflate data is
   invalid or incomplete, Z_VERSION_ERROR if the version of zlib.h and
   the version of the library linked do not match, or Z_ERRNO if there
   is an error reading or writing the files. */
static off_t inf(int dest, int source, off_t source_size)
{
    int ret;
    unsigned have;
    z_stream strm;
    unsigned char in[CHUNK * 1024];
    unsigned char out[CHUNK * 1024];

    /* allocate inflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.avail_in = 0;
    strm.next_in = Z_NULL;
    ret = inflateInit2(&strm, -15);
    if (ret != Z_OK)
        return ret;

    /* decompress until deflate stream ends or end of file */
    do {
        ssize_t rd = safe_read(source, in, CHUNK * 1024);
        if(rd < 0) {
            fprintf(stderr, "error: read(): %s\n", strerror(errno));
            (void)inflateEnd(&strm);
            return Z_ERRNO;
        }
        if (rd == 0)
            break;
        strm.avail_in = rd; 
        strm.next_in = in;

        /* run inflate() on input until output buffer not full */
        do {
            strm.avail_out = CHUNK * 1024;
            strm.next_out = out;
            ret = inflate(&strm, Z_NO_FLUSH);
            switch (ret) {
            case Z_NEED_DICT:
                ret = Z_DATA_ERROR;     /* and fall through */
            case Z_DATA_ERROR:                                                                                                                                                                   
            case Z_MEM_ERROR:
                (void)inflateEnd(&strm);
                return ret;
            }
            have = (CHUNK * 1024) - strm.avail_out;
            if (write(dest, out, have) < 0) {
                (void)inflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);
    
        /* done when inflate() says it's done */
    } while (ret != Z_STREAM_END);

    /* clean up and return */
    (void)inflateEnd(&strm);
    return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}   

static off_t copyfd_to_eof(int dst_fd, int src_fd, off_t size)
{
    int status = -1;
    off_t total = 0;
    char buffer[CHUNK * 1024];
    unsigned int buffer_size = CHUNK * 1024;
#if 0
    char *buffer;
    unsigned int buffer_size;

    /* We want page-aligned buffer, just in case kernel is clever
     * and can do page-aligned io more efficiently */
    buffer = mmap(NULL, CONFIG_FEATURE_COPYBUF_KB * 1024,
            PROT_READ | PROT_WRITE,
            MAP_PRIVATE | MAP_ANON,
            /* ignored: */ -1, 0);
    buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024;
    if (buffer == MAP_FAILED) {
        buffer = alloca(4 * 1024);
        buffer_size = 4 * 1024;
    }
#endif

    if (src_fd < 0)
        goto out;

    if (!size) {
        size = buffer_size;
        status = 1; /* copy until eof */
    }

    while (1) {
        ssize_t wr, rd = safe_read(src_fd, buffer, size > buffer_size ? buffer_size : size);
        if (!rd) { /* eof - all done */
            status = 0;
            break;
        }
        if (rd < 0) {
            fprintf(stderr, "error: read(): %s\n", strerror(errno));
            break;
        }
        wr = write(dst_fd, buffer, rd);
        if (wr < rd) {
            fprintf(stderr, "warning: partial write: %ld < %ld\n", wr, rd);
        }
        total += rd;
        if (status < 0) { /* if we aren't copying till EOF... */
            size -= rd;
            if (!size) {
                /* 'size' bytes copied - all done */
                status = 0;
                break;
            }
        }
    }

 out:
#if 0
    if (buffer_size != 4 * 1024)
        munmap(buffer, buffer_size);
#endif
    return status ? -1 : total;
}

/* No getopt required */
int main(int argc, char **argv)
{
	unsigned char magic[2];
	struct rpm_lead lead;
    unsigned int pos;
	int r, rpm_fd, out_fd = 1;

	if (argc == 1) {
		rpm_fd = 1;
	} else {
		rpm_fd = open(argv[1], O_RDONLY);
        if (rpm_fd < 0) {
            fprintf(stderr, "rpm2cpio: error opening %s: %s\n", argv[1], strerror(errno));
            return -1;
        }
	}

	read(rpm_fd, &lead, sizeof(struct rpm_lead));
    /* Just check the magic, the rest is irrelevant */
    if (lead.magic != RPM_LEAD_MAGIC) {
        fprintf(stderr, "rpm2cpio: error: invalid RPM magic: 0x%08x != 0x%08x\n", lead.magic, RPM_LEAD_MAGIC);
        return -1;
    }

	/* Skip the signature header */
	pos = skip_header(rpm_fd);
	lseek(rpm_fd, (8 - (pos & 7)) & 7, SEEK_CUR);
    //lseek(rpm_fd, (-(int)pos) & 7, SEEK_CUR);

	/* Skip the main header */
	skip_header(rpm_fd);

	read(rpm_fd, &magic, 2);
	if ((magic[0] != 0x1f) || (magic[1] != 0x8b)) {
		fprintf(stderr, "rpm2cpio: error: invalid gzip magic, dumping raw compressed image.\n");
        copyfd_to_eof(out_fd, rpm_fd, 0);
        goto ret;
	}

    skip_gzip_header(rpm_fd);
	if ((r = inf(out_fd, rpm_fd, 0)) != Z_OK) {
        fprintf(stderr, "rpm2cpio: error while inflating: %s\n",
                ((r != Z_ERRNO) ? zlib_errstr(r) : strerror(errno)));
	}

ret:
	close(rpm_fd);
	return 0;
}