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diff --git a/inflate.3 b/inflate.3 new file mode 100644 index 00000000..255e0f84 --- /dev/null +++ b/inflate.3 @@ -0,0 +1,398 @@ +.Dd January 15, 2017 +.Dt INFLATE 3 +.Os +. +.Sh NAME +.Nm inflate +.Nd deflate decompression +. +.Sh LIBRARY +.Lb libz +. +.Sh SYNOPSIS +.In zlib.h +.Ft int +.Fn inflate "z_streamp strm" "int flush" +. +.Sh DESCRIPTION +.Fn inflate +decompresses as much data as possible, +and stops when the input buffer becomes empty +or the output buffer becomes full. +It may introduce some output latency +(reading input without producing any output) +except when forced to flush. +. +.Pp +The detailed semantics are as follows. +.Fn inflate +performs one or both of the following actions: +. +.Bl -dash +.It +Decompress more input starting at +.Fa next_in +and update +.Fa next_in +and +.Fa avail_in +accordingly. +If not all input can be processed +(because there is not enough room in the output buffer), +then +.Fa next_in +and +.Fa avail_in +are updated accordingly, +and processing will resume at this point +for the next call of +.Fn inflate . +. +.It +Generate more output starting at +.Fa next_out +and update +.Fa next_out +and +.Fa avail_out +accordingly. +.Fn inflate +provides as much output as possible, +until there is no more input data +or no more space in the output buffer +.Po +see below about the +.Fa flush +parameter +.Pc . +.El +. +.Pp +Before the call of +.Fn inflate , +the application should ensure that +at least one of the actions is possible, +by providing more input +and/or consuming more output, +and updating the +.Fa next_* +and +.Fa avail_* +values accordingly. +If the caller of +.Fn inflate +does not provide both available input +and available output space, +it is possible that there will be no progress made. +The application can consume the uncompressed output +when it wants, +for example when the output buffer is full +.Po +.Fa avail_out +== 0 +.Pc , +or after each call of +.Fn inflate . +If +.Fn inflate +returns +.Dv Z_OK +and with zero +.Fa avail)out , +it must be called again after making room +in the output buffer +because there might be more output pending. +. +.Pp +The +.Fa flush +parameter of +.Fn inflate +can be +.Dv Z_NO_FLUSH , +.Dv Z_SYNC_FLUSH , +.Dv Z_FINISH , +.Dv Z_BLOCK , +or +.Dv Z_TREES . +.Dv Z_SYNC_FLUSH +requests that +.Fn inflate +flush as much output as possible +to the output buffer. +.Dv Z_BLOCK +requests that +.Fn inflate +stop if and when it gets to the next deflate block boundary. +When decoding the zlib or gzip format, +this will cause +.Fn inflate +to return immediately after the header +and before the first block. +When doing a raw inflate, +.Fn inflate +will go ahead and process the first block, +and will return when it gets to the end of that block, +or when it runs out of data. +. +.Pp +The +.Dv Z_BLOCK +option assists in appending to +or combining deflate streams. +To assist in this, +on return +.Fn inflate +always sets +.Fa strm->data_type +to the number of unused bits +in the last byte taken from +.Fa strm->next_in , +plus 64 if +.Fn inflate +is currently decoding the last block in the deflate stream, +plus 128 if +.Fn inflate +returned immediately after decoding an end-of-block code +or decoding the complete header up to +just before the first byte of the deflate stream. +The end-of-block will not be indicated +until all of the uncompressed data +from that block has been written to +.Fa strm->next_out . +The number of unused bits may in general be greater than seven, +except when bit 7 of +.Fa data_type +is set, +in which case the number of unused bits +will be less than eight. +.Fa data_type +is set as noted here every time +.Fn inflate +returns for all flush options, +and so can be used to determine +the amount of currently consumed input in bits. +. +.Pp +The +.Dv Z_TREES +option behaves as +.Dv Z_BLOCK +does, +but it also returns +when the end of each deflate block header is reached, +before any actual data in that block is decoded. +This allows the caller to determine +the length of the deflate block header +for later use in random access +within a deflate block. +256 is added to the value of +.Fa strm->data_type +when +.Fn inflate +returns immediately after reaching +the end of the deflate block header. +. +.Pp +.Fn inflate +should normally be called until it returns +.Dv Z_STREAM_END +or an error. +However if all decompression is to be performed +in a single step +.Po +a single call of +.Fn inflate +.Pc , +the parameter +.Fa flush +should be set to +.Dv Z_FINISH . +In this case all pending input is processed +and all pending output is flushed; +.Fa avail_out +must be large enough to hold all of +the uncompressed data for the operation to complete. +(The size of the uncompressed data +may have been saved by the compressor for this purpose.) +The use of +.Dv Z_FINISH +is not required to perform inflation in one step. +However it may be used to inform +.Fn inflate +that a faster approach can be used for the single +.Fn inflate +call. +.Dv Z_FINISH also informs +.Fn inflate +to not maintain a sliding window +if the stream completes, +which reduces +.Fn inflate Ap s +memory footprint. +If the stream does not complete, +either because not all of the stream is provided +or not enough output space is provided, +then a sliding window will be allocated and +.Fn inflate +can be called again to continue the operation as if +.Dv Z_NO_FLUSH +had been used. +. +.Pp +In this implementation, +.Fn inflate +always flushes as much output as possible +to the output buffer, +and always uses the faster approach +on the first call. +So the effects of the +.Fa flush +parameter in this implementation +are on the return value of +.Fn inflate +as noted below, +when +.Fn inflate +returns early when +.Dv Z_BLOCK +or +.Dv Z_TREES +is used, +and when +.Fn inflate +avoids the allocation of memory +for a sliding window when +.Dv Z_FINISH +is used. +. +.Pp +If a preset dictionary is needed after this call +.Po +see +.Xr inflateSetDictionary 3 +.Pc , +.Fn inflate +sets +.Fa strm->adler +to the Adler-32 checksum of the dictionary +chosen by the compressor +and returns +.Dv Z_NEED_DICT ; +otherwise it sets +.Fa strm->adler +to the Adler-32 checksum +of all output produced so far +.Po +that is, +.Fa total_out +bytes +.Pc +and returns +.Dv Z_OK , +.Dv Z_STREAM_END +or an error code +as described in +.Sx RETURN VALUES . +At the end of the stream, +.Fn inflate +checks that its computed Adler-32 checksum +is equal to that saved by the compressor +and returns +.Dv Z_STREAM_END +only if the checksum is correct. +. +.Pp +.Fn inflate +can decompress and check +either zlib-wrapped or gzip-wrapped +deflate data. +The header type is detected automatically, +if requested when initializing with +.Xr inflateInit2 3 . +Any information contained in the gzip header +is not retained unless +.Xr inflateGetHeader 3 +is used. +When processing gzip-wrapped deflate data, +.Fa strm->adler32 +is set to the CRC-32 +of the output produced so far. +The CRC-32 is checked against the gzip trailer, +as is the uncompressed length, +modulo 2^32. +. +.Sh RETURN VALUES +.Fn inflate +returns +.Dv Z_OK +if some progress has been made +(more input processed or more output produced), +.Dv Z_STREAM_END +if the end of the compressed data has been reached +and all uncompressed output has been produced, +.Dv Z_NEED_DICT +if a preset dictionary is needed at this point, +.Dv Z_DATA_ERROR +if the input data was corrupted +.Po +input stream not conforming to the zlib format +or incorrect check value, +in which case +.Fa strm->msg +points to a string with a more specific error +.Pc , +.Dv Z_STREAM_ERROR +if the stream structure was inconsistent +.Po +for example +.Fa next_in +or +.Fa next_out +was +.Dv Z_NULL , +or the state was inadvertently written over +by the application +.Pc , +.Dv Z_MEM_ERROR +if there was not enough memory, +.Dv Z_BUF_ERROR +if no progress was possible +or if there was not enough room +in the output buffer when +.Dv Z_FINISH +is used. +Note that +.Dv Z_BUF_ERROR +is not fatal, +and +.Fn inflate +can be called again with more input +and more output space +to continue decompressing. +If +.Dv Z_DATA_ERROR +is returned, +the application may then call +.Xr inflateSync 3 +to look for a good compression block +if a partial recovery of the data +is to be attempted. +. +.Sh SEE ALSO +.Xr deflate 3 , +.Xr inflateBack 3 , +.Xr inflateEnd 3 , +.Xr inflateInit 3 , +.Xr inflateMark 3 , +.Xr inflateSync 3 +. +.Sh HISTORY +This manual page was converted from +.In zlib.h +to mdoc format by +.An June McEnroe Aq Mt june@causal.agency . +. +.Sh AUTHORS +.An Jean-loup Gailly Aq Mt jloup@gzip.org +.An Mark Adler Aq Mt madler@alumni.caltech.edu |