/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2004, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * $Id: content_encoding.c,v 1.17 2004/07/04 21:53:46 bagder Exp $
 ***************************************************************************/

#include "setup.h"

#ifdef HAVE_LIBZ

#include <stdlib.h>
#include <string.h>

#include "urldata.h"
#include <curl/curl.h>
#include "sendf.h"
#include "content_encoding.h"
#include "memory.h"

#include "memdebug.h"

#define DSIZ 0x10000             /* buffer size for decompressed data */

#define GZIP_MAGIC_0 0x1f
#define GZIP_MAGIC_1 0x8b

/* gzip flag byte */
#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define COMMENT      0x10 /* bit 4 set: file comment present */
#define RESERVED     0xE0 /* bits 5..7: reserved */

static CURLcode
process_zlib_error( struct SessionHandle *data, z_stream *z ) {
	if ( z->msg ) {
		failf( data, "Error while processing content unencoding.\n%s",
			   z->msg );
	} else {
		failf( data, "Error while processing content unencoding.\n"
					 "Unknown failure within decompression software." );
	}

	return CURLE_BAD_CONTENT_ENCODING;
}

static CURLcode
exit_zlib( z_stream *z, bool *zlib_init, CURLcode result ) {
	inflateEnd( z );
	*zlib_init = 0;
	return result;
}

CURLcode
Curl_unencode_deflate_write( struct SessionHandle *data,
							 struct Curl_transfer_keeper *k,
							 ssize_t nread ) {
	int status;                 /* zlib status */
	CURLcode result = CURLE_OK; /* Curl_client_write status */
	char decomp[DSIZ];          /* Put the decompressed data here. */
	z_stream *z = &k->z;        /* zlib state structure */

	/* Initialize zlib? */
	if ( !k->zlib_init ) {
		z->zalloc = (alloc_func)Z_NULL;
		z->zfree = (free_func)Z_NULL;
		z->opaque = 0;
		z->next_in = NULL;
		z->avail_in = 0;
		if ( inflateInit( z ) != Z_OK ) {
			return process_zlib_error( data, z );
		}
		k->zlib_init = 1;
	}

	/* Set the compressed input when this function is called */
	z->next_in = (Bytef *)k->str;
	z->avail_in = (uInt)nread;

	/* because the buffer size is fixed, iteratively decompress
	   and transfer to the client via client_write. */
	for (;; ) {
		/* (re)set buffer for decompressed output for every iteration */
		z->next_out = (Bytef *)&decomp[0];
		z->avail_out = DSIZ;

		status = inflate( z, Z_SYNC_FLUSH );
		if ( status == Z_OK || status == Z_STREAM_END ) {
			if ( DSIZ - z->avail_out ) {
				result = Curl_client_write( data, CLIENTWRITE_BODY, decomp,
											DSIZ - z->avail_out );
				/* if !CURLE_OK, clean up, return */
				if ( result ) {
					return exit_zlib( z, &k->zlib_init, result );
				}
			}

			/* Done?; clean up, return */
			if ( status == Z_STREAM_END ) {
				if ( inflateEnd( z ) == Z_OK ) {
					return exit_zlib( z, &k->zlib_init, result );
				} else {
					return exit_zlib( z, &k->zlib_init, process_zlib_error( data, z ) );
				}
			}

			/* Done with these bytes, exit */
			if ( status == Z_OK && z->avail_in == 0 && z->avail_out > 0 ) {
				return result;
			}
		} else {                /* Error; exit loop, handle below */
			return exit_zlib( z, &k->zlib_init, process_zlib_error( data, z ) );
		}
	}
}

/* Skip over the gzip header */
static enum {
	GZIP_OK,
	GZIP_BAD,
	GZIP_UNDERFLOW
} check_gzip_header( unsigned char const *data, ssize_t len, ssize_t *headerlen )
{
	int method, flags;
	const ssize_t totallen = len;

	/* The shortest header is 10 bytes */
	if ( len < 10 ) {
		return GZIP_UNDERFLOW;
	}

	if ( ( data[0] != GZIP_MAGIC_0 ) || ( data[1] != GZIP_MAGIC_1 ) ) {
		return GZIP_BAD;
	}

	method = data[2];
	flags = data[3];

	if ( method != Z_DEFLATED || ( flags & RESERVED ) != 0 ) {
		/* Can't handle this compression method or unknown flag */
		return GZIP_BAD;
	}

	/* Skip over time, xflags, OS code and all previous bytes */
	len -= 10;
	data += 10;

	if ( flags & EXTRA_FIELD ) {
		ssize_t extra_len;

		if ( len < 2 ) {
			return GZIP_UNDERFLOW;
		}

		extra_len = ( data[1] << 8 ) | data[0];

		if ( len < ( extra_len + 2 ) ) {
			return GZIP_UNDERFLOW;
		}

		len -= ( extra_len + 2 );
	}

	if ( flags & ORIG_NAME ) {
		/* Skip over NUL-terminated file name */
		while ( len && *data ) {
			--len;
			++data;
		}
		if ( !len || *data ) {
			return GZIP_UNDERFLOW;
		}

		/* Skip over the NUL */
		--len;
		++data;
	}

	if ( flags & COMMENT ) {
		/* Skip over NUL-terminated comment */
		while ( len && *data ) {
			--len;
			++data;
		}
		if ( !len || *data ) {
			return GZIP_UNDERFLOW;
		}

		/* Skip over the NUL */
		--len;
		++data;
	}

	if ( flags & HEAD_CRC ) {
		if ( len < 2 ) {
			return GZIP_UNDERFLOW;
		}

		len -= 2;
		data += 2;
	}

	*headerlen = totallen - len;
	return GZIP_OK;
}

CURLcode
Curl_unencode_gzip_write( struct SessionHandle *data,
						  struct Curl_transfer_keeper *k,
						  ssize_t nread ) {
	int status;                 /* zlib status */
	CURLcode result = CURLE_OK; /* Curl_client_write status */
	char decomp[DSIZ];          /* Put the decompressed data here. */
	z_stream *z = &k->z;        /* zlib state structure */

	/* Initialize zlib? */
	if ( !k->zlib_init ) {
		z->zalloc = (alloc_func)Z_NULL;
		z->zfree = (free_func)Z_NULL;
		z->opaque = 0;
		z->next_in = NULL;
		z->avail_in = 0;
		if ( inflateInit2( z, -MAX_WBITS ) != Z_OK ) {
			return process_zlib_error( data, z );
		}
		k->zlib_init = 1; /* Initial call state */
	}

	/* This next mess is to get around the potential case where there isn't
	 * enough data passed in to skip over the gzip header.  If that happens, we
	 * malloc a block and copy what we have then wait for the next call.  If
	 * there still isn't enough (this is definitely a worst-case scenario), we
	 * make the block bigger, copy the next part in and keep waiting.
	 */

	/* Skip over gzip header? */
	if ( k->zlib_init == 1 ) {
		/* Initial call state */
		ssize_t hlen;

		switch ( check_gzip_header( (unsigned char *)k->str, nread, &hlen ) ) {
		case GZIP_OK:
			z->next_in = (Bytef *)k->str + hlen;
			z->avail_in = (uInt)( nread - hlen );
			k->zlib_init = 3; /* Inflating stream state */
			break;

		case GZIP_UNDERFLOW:
			/* We need more data so we can find the end of the gzip header.  It's
			 * possible that the memory block we malloc here will never be freed if
			 * the transfer abruptly aborts after this point.  Since it's unlikely
			 * that circumstances will be right for this code path to be followed in
			 * the first place, and it's even more unlikely for a transfer to fail
			 * immediately afterwards, it should seldom be a problem.
			 */
			z->avail_in = (uInt)nread;
			z->next_in = malloc( z->avail_in );
			if ( z->next_in == NULL ) {
				return exit_zlib( z, &k->zlib_init, CURLE_OUT_OF_MEMORY );
			}
			memcpy( z->next_in, k->str, z->avail_in );
			k->zlib_init = 2; /* Need more gzip header data state */
			/* We don't have any data to inflate yet */
			return CURLE_OK;

		case GZIP_BAD:
		default:
			return exit_zlib( z, &k->zlib_init, process_zlib_error( data, z ) );
		}

	} else if ( k->zlib_init == 2 )     {
		/* Need more gzip header data state */
		ssize_t hlen;
		unsigned char *oldblock = z->next_in;

		z->avail_in += nread;
		z->next_in = realloc( z->next_in, z->avail_in );
		if ( z->next_in == NULL ) {
			free( oldblock );
			return exit_zlib( z, &k->zlib_init, CURLE_OUT_OF_MEMORY );
		}
		/* Append the new block of data to the previous one */
		memcpy( z->next_in + z->avail_in - nread, k->str, nread );

		switch ( check_gzip_header( z->next_in, z->avail_in, &hlen ) ) {
		case GZIP_OK:
			/* This is the zlib stream data */
			free( z->next_in );
			/* Don't point into the malloced block since we just freed it */
			z->next_in = (Bytef *)k->str + hlen + nread - z->avail_in;
			z->avail_in = (uInt)( z->avail_in - hlen );
			k->zlib_init = 3; /* Inflating stream state */
			break;

		case GZIP_UNDERFLOW:
			/* We still don't have any data to inflate! */
			return CURLE_OK;

		case GZIP_BAD:
		default:
			free( z->next_in );
			return exit_zlib( z, &k->zlib_init, process_zlib_error( data, z ) );
		}

	} else {
		/* Inflating stream state */
		z->next_in = (Bytef *)k->str;
		z->avail_in = (uInt)nread;
	}

	if ( z->avail_in == 0 ) {
		/* We don't have any data to inflate; wait until next time */
		return CURLE_OK;
	}

	/* because the buffer size is fixed, iteratively decompress and transfer to
	   the client via client_write. */
	for (;; ) {
		/* (re)set buffer for decompressed output for every iteration */
		z->next_out = (Bytef *)&decomp[0];
		z->avail_out = DSIZ;

		status = inflate( z, Z_SYNC_FLUSH );
		if ( status == Z_OK || status == Z_STREAM_END ) {
			if ( DSIZ - z->avail_out ) {
				result = Curl_client_write( data, CLIENTWRITE_BODY, decomp,
											DSIZ - z->avail_out );
				/* if !CURLE_OK, clean up, return */
				if ( result ) {
					return exit_zlib( z, &k->zlib_init, result );
				}
			}

			/* Done?; clean up, return */
			/* We should really check the gzip CRC here */
			if ( status == Z_STREAM_END ) {
				if ( inflateEnd( z ) == Z_OK ) {
					return exit_zlib( z, &k->zlib_init, result );
				} else {
					return exit_zlib( z, &k->zlib_init, process_zlib_error( data, z ) );
				}
			}

			/* Done with these bytes, exit */
			if ( status == Z_OK && z->avail_in == 0 && z->avail_out > 0 ) {
				return result;
			}
		} else {                /* Error; exit loop, handle below */
			return exit_zlib( z, &k->zlib_init, process_zlib_error( data, z ) );
		}
	}
}
#endif /* HAVE_LIBZ */
