/*
 * zlib wrappers to make sure we don't silently miss errors
 * at init time.
 */
#include "cache.h"

static const char *zerr_to_string(int status)
{
        switch (status) {
        case Z_MEM_ERROR:
                return "out of memory";
        case Z_VERSION_ERROR:
                return "wrong version";
        case Z_NEED_DICT:
                return "needs dictionary";
        case Z_DATA_ERROR:
                return "data stream error";
        case Z_STREAM_ERROR:
                return "stream consistency error";
        default:
                return "unknown error";
        }
}

/*
 * avail_in and avail_out in zlib are counted in uInt, which typically
 * limits the size of the buffer we can use to 4GB when interacting
 * with zlib in a single call to inflate/deflate.
 */
/* #define ZLIB_BUF_MAX ((uInt)-1) */
#define ZLIB_BUF_MAX ((uInt) 1024 * 1024 * 1024) /* 1GB */
static inline uInt zlib_buf_cap(unsigned long len)
{
        return (ZLIB_BUF_MAX < len) ? ZLIB_BUF_MAX : len;
}

static void zlib_pre_call(git_zstream *s)
{
        s->z.next_in = s->next_in;
        s->z.next_out = s->next_out;
        s->z.total_in = s->total_in;
        s->z.total_out = s->total_out;
        s->z.avail_in = zlib_buf_cap(s->avail_in);
        s->z.avail_out = zlib_buf_cap(s->avail_out);
}

static void zlib_post_call(git_zstream *s)
{
        unsigned long bytes_consumed;
        unsigned long bytes_produced;

        bytes_consumed = s->z.next_in - s->next_in;
        bytes_produced = s->z.next_out - s->next_out;
        if (s->z.total_out != s->total_out + bytes_produced)
                die("BUG: total_out mismatch");
        if (s->z.total_in != s->total_in + bytes_consumed)
                die("BUG: total_in mismatch");

        s->total_out = s->z.total_out;
        s->total_in = s->z.total_in;
        s->next_in = s->z.next_in;
        s->next_out = s->z.next_out;
        s->avail_in -= bytes_consumed;
        s->avail_out -= bytes_produced;
}

void git_inflate_init(git_zstream *strm)
{
        int status;

        zlib_pre_call(strm);
        status = inflateInit(&strm->z);
        zlib_post_call(strm);
        if (status == Z_OK)
                return;
        die("inflateInit: %s (%s)", zerr_to_string(status),
            strm->z.msg ? strm->z.msg : "no message");
}

void git_inflate_init_gzip_only(git_zstream *strm)
{
        /*
         * Use default 15 bits, +16 is to accept only gzip and to
         * yield Z_DATA_ERROR when fed zlib format.
         */
        const int windowBits = 15 + 16;
        int status;

        zlib_pre_call(strm);
        status = inflateInit2(&strm->z, windowBits);
        zlib_post_call(strm);
        if (status == Z_OK)
                return;
        die("inflateInit2: %s (%s)", zerr_to_string(status),
            strm->z.msg ? strm->z.msg : "no message");
}

void git_inflate_end(git_zstream *strm)
{
        int status;

        zlib_pre_call(strm);
        status = inflateEnd(&strm->z);
        zlib_post_call(strm);
        if (status == Z_OK)
                return;
        error("inflateEnd: %s (%s)", zerr_to_string(status),
              strm->z.msg ? strm->z.msg : "no message");
}

int git_inflate(git_zstream *strm, int flush)
{
        int status;

        for (;;) {
                zlib_pre_call(strm);
                /* Never say Z_FINISH unless we are feeding everything */
                status = inflate(&strm->z,
                                 (strm->z.avail_in != strm->avail_in)
                                 ? 0 : flush);
                if (status == Z_MEM_ERROR)
                        die("inflate: out of memory");
                zlib_post_call(strm);

                /*
                 * Let zlib work another round, while we can still
                 * make progress.
                 */
                if ((strm->avail_out && !strm->z.avail_out) &&
                    (status == Z_OK || status == Z_BUF_ERROR))
                        continue;
                break;
        }

        switch (status) {
        /* Z_BUF_ERROR: normal, needs more space in the output buffer */
        case Z_BUF_ERROR:
        case Z_OK:
        case Z_STREAM_END:
                return status;
        default:
                break;
        }
        error("inflate: %s (%s)", zerr_to_string(status),
              strm->z.msg ? strm->z.msg : "no message");
        return status;
}

#if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
#define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
#endif

unsigned long git_deflate_bound(git_zstream *strm, unsigned long size)
{
        return deflateBound(&strm->z, size);
}

void git_deflate_init(git_zstream *strm, int level)
{
        int status;

        zlib_pre_call(strm);
        status = deflateInit(&strm->z, level);
        zlib_post_call(strm);
        if (status == Z_OK)
                return;
        die("deflateInit: %s (%s)", zerr_to_string(status),
            strm->z.msg ? strm->z.msg : "no message");
}

void git_deflate_init_gzip(git_zstream *strm, int level)
{
        /*
         * Use default 15 bits, +16 is to generate gzip header/trailer
         * instead of the zlib wrapper.
         */
        const int windowBits = 15 + 16;
        int status;

        zlib_pre_call(strm);
        status = deflateInit2(&strm->z, level,
                                  Z_DEFLATED, windowBits,
                                  8, Z_DEFAULT_STRATEGY);
        zlib_post_call(strm);
        if (status == Z_OK)
                return;
        die("deflateInit2: %s (%s)", zerr_to_string(status),
            strm->z.msg ? strm->z.msg : "no message");
}

void git_deflate_end(git_zstream *strm)
{
        int status;

        zlib_pre_call(strm);
        status = deflateEnd(&strm->z);
        zlib_post_call(strm);
        if (status == Z_OK)
                return;
        error("deflateEnd: %s (%s)", zerr_to_string(status),
              strm->z.msg ? strm->z.msg : "no message");
}

int git_deflate_end_gently(git_zstream *strm)
{
        int status;

        zlib_pre_call(strm);
        status = deflateEnd(&strm->z);
        zlib_post_call(strm);
        return status;
}

int git_deflate(git_zstream *strm, int flush)
{
        int status;

        for (;;) {
                zlib_pre_call(strm);

                /* Never say Z_FINISH unless we are feeding everything */
                status = deflate(&strm->z,
                                 (strm->z.avail_in != strm->avail_in)
                                 ? 0 : flush);
                if (status == Z_MEM_ERROR)
                        die("deflate: out of memory");
                zlib_post_call(strm);

                /*
                 * Let zlib work another round, while we can still
                 * make progress.
                 */
                if ((strm->avail_out && !strm->z.avail_out) &&
                    (status == Z_OK || status == Z_BUF_ERROR))
                        continue;
                break;
        }

        switch (status) {
        /* Z_BUF_ERROR: normal, needs more space in the output buffer */
        case Z_BUF_ERROR:
        case Z_OK:
        case Z_STREAM_END:
                return status;
        default:
                break;
        }
        error("deflate: %s (%s)", zerr_to_string(status),
              strm->z.msg ? strm->z.msg : "no message");
        return status;
}