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/*
 * Helper functions to handle compression via zlib
 *
 * Copyright (C) 2007-2008 Julian Brown
 * Copyright (C) 2008 Mike Frysinger
 *
 * Licensed under the GPL-2 or later.
 */

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

#include <zlib.h>
#include "compress.h"
#include "stubs.h"

/* Open an (uncompressed) file as a stream.  Return 0 on success, 1 on
   error.
   NOTE: The MODE argument must remain valid for the lifetime of the stream,
   because it is referred to by reopen_stream_compressed() if it is called.
   String constants work fine.  */

int
fopen_stream_u(stream *fp, const char *path, const char *mode)
{
        fp->u.filep = fopen(path, mode);
        fp->type = (fp->u.filep) ? UNCOMPRESSED : INVALID;
        fp->mode = mode;
        return (fp->u.filep) ? 0 : 1;
}

/* Read from stream.  Return number of elements read.  */

size_t
fread_stream(void *ptr, size_t size, size_t nmemb, stream *str)
{
        size_t read;

        switch (str->type) {
                case UNCOMPRESSED:
                read = fread(ptr, size, nmemb, str->u.filep);
                break;

                case COMPRESSED:
                read = gzread(str->u.gzfilep, ptr, size * nmemb) / size;
                break;

                default:
                abort();
        }

        return read;
}

/* Write to stream.  Return number of elements written.  */

size_t
fwrite_stream(const void *ptr, size_t size, size_t nmemb, stream *str)
{
        size_t written;

        switch (str->type) {
                case UNCOMPRESSED:
                written = fwrite(ptr, size, nmemb, str->u.filep);
                break;

                case COMPRESSED:
                written = gzwrite(str->u.gzfilep, ptr, size * nmemb) / size;
                break;

                default:
                abort();
        }

        return written;
}

/* Close stream.  */

int
fclose_stream(stream *str)
{
        switch (str->type) {
                case UNCOMPRESSED:
                return fclose(str->u.filep);

                case COMPRESSED:
                return gzclose(str->u.gzfilep);

                default:
                abort();
        }

        return 0;
}

int
ferror_stream(stream *str)
{
        switch (str->type) {
                case UNCOMPRESSED:
                return ferror(str->u.filep);

                case COMPRESSED:
                {
                        const char *err;
                        int errno;

                        err = gzerror(str->u.gzfilep, &errno);
                        if (errno == Z_OK || errno == Z_STREAM_END)
                                return 0;
                        else if (errno == Z_ERRNO)
                                return 1;
                        else {
                                fprintf(stderr, "%s\n", err);
                                return 1;
                        }
                }
                break;

                default:
                abort();
        }

        return 0;
}

int
fseek_stream(stream *str, long offset, int whence)
{
        switch (str->type) {
                case UNCOMPRESSED:
                return fseek(str->u.filep, offset, whence);

                case COMPRESSED:
                return gzseek(str->u.gzfilep, offset, whence);

                default:
                abort();
        }
}

/* Reopen a stream at the current file position.  */

void
reopen_stream_compressed(stream *str)
{
        int fd;
        long offset, roffset;

        /* Already a compressed stream, return immediately  */
        if (str->type == COMPRESSED)
                return;

        if (str->type == INVALID)
                abort();

        fd = fileno(str->u.filep);
        /* Get current (buffered) file position.  */
        offset = ftell(str->u.filep);

        /* Make sure there's nothing left in buffers.  */
        fflush(str->u.filep);

        /* Reposition underlying FD.  (Might be unnecessary?)  */
        roffset = lseek(fd, offset, SEEK_SET);

        assert(roffset == offset);

        /* Reopen as compressed stream.  */
        str->u.gzfilep = gzdopen(fd, str->mode);
        gzsetparams(str->u.gzfilep, 9, Z_DEFAULT_STRATEGY);
        str->type = COMPRESSED;
}

void
transfer(stream *ifp, stream *ofp, int count)
{
        char cmd[1024];
        int n, num;

        while (count == -1 || count > 0) {
                if (count == -1 || count > sizeof(cmd))
                        num = sizeof(cmd);
                else
                        num = count;
                n = fread_stream(cmd, 1, num, ifp);
                if (n == 0)
                        break;
                if (fwrite_stream(cmd, n, 1, ofp) != 1)
                        fatal_perror("Write failed :-(\n");
                if (count != -1)
                        count -= n;
        }
        if (count > 0)
                fatal("Failed to transfer %d bytes\n", count);
}