The operations that are allowed on the stream and how these are performed are defined by the mode parameter. The returned stream is fully buffered by default if it is known to not refer to an interactive device see setbuf. The returned pointer can be disassociated from the file by calling fclose or freopen.
Usage Example We often get questions about how the deflate and inflate functions should be used. So for those who have read zlib.
The annotations are interspersed between lines of the code. So please read between the lines. We hope this helps explain some of the intricacies of zlib. Without further ado, here is the program zpipe. Without this, those systems would assume that the input and output files are text, and try to convert the end-of-line characters from one standard to another.
That would corrupt binary data, and in particular would render the compressed data unusable. This sets the input and output to binary which suppresses the end-of-line conversions. Larger buffer sizes would be more efficient, especially for inflate. If the memory is available, buffers sizes on the order of K or K bytes should be used.
The output data will be in the zlib format, which is different from the gzip or zip formats. The zlib format has a very small header of only two bytes to identify it as a zlib stream and to provide decoding information, and a four-byte trailer with a fast check value to verify the integrity of the uncompressed data after decoding.
The strm structure is used to pass information to and from the zlib routines, and to maintain the deflate state. This must be done before the first use of deflate.
The zalloc, zfree, and opaque fields in the strm structure must be initialized before calling deflateInit.
An application may also choose to provide custom memory allocation routines here. Php fputs vs fwrite api zlib Technical Details. Lower compression levels result in faster execution, but less compression.
Higher levels result in greater compression, but slower execution. Level 0 actually does no compression at all, and in fact expands the data slightly to produce the zlib format it is not a byte-for-byte copy of the input. More advanced applications of zlib may use deflateInit2 here instead.
Such an application may want to reduce how much memory will be used, at some price in compression. Or it may need to request a gzip header and trailer instead of a zlib header and trailer, or raw encoding with no header or trailer at all. This is especially important for environments in which zlib is a shared library.
Note that an application can initialize multiple, independent zlib streams, which can operate in parallel. The state information maintained in the structure allows the zlib routines to be reentrant.
The outer do-loop reads all of the input file and exits at the bottom of the loop once end-of-file is reached. This loop contains the only call of deflate. So we must make sure that all of the input data has been processed and that all of the output data has been generated and consumed before we fall out of the loop at the bottom.
We also check to see if end-of-file on the input has been reached using feof. If there is an error in reading from the input file, the process is aborted with deflateEnd being called to free the allocated zlib state before returning the error. We wouldn't want a memory leak, now would we?
Once that's done, deflateInit or deflateInit2 would have to be called to start a new compression process. There is no point here in checking the deflateEnd return code.
The deallocation can't fail. Once there is no more new output, deflate is guaranteed to have consumed all of the input, i. Those counters and pointers are then updated past the input data consumed and the output data written.
It is the amount of output space available that may limit how much input is consumed. Hence the inner loop to make sure that all of the input is consumed by providing more output space each time.
The parameters to deflate are a pointer to the strm structure containing the input and output information and the internal compression engine state, and a parameter indicating whether and how to flush data to the output. Normally deflate will consume several K bytes of input data before producing any output except for the headerin order to accumulate statistics on the data for optimum compression.
It will then put out a burst of compressed data, and proceed to consume more input before the next burst.
Eventually, deflate must be told to terminate the stream, complete the compression with provided input data, and write out the trailer check value. However depending on how much output space is provided, deflate may have to be called several times until it has provided the complete compressed stream, even after it has consumed all of the input.PHP file_get_contents() Function The file_get_contents() reads a file into a string.
This function is the preferred way to read the contents of a file into a string. Because it will use memory mapping techniques, if this is supported by the server, to enhance performance. It's intended to automatically switch to using FTP credentials where the filesystem is read-only to the PHP process, as a result of that, it's not viable to use during say a caching plugin, random REST API calls (Unless specifically for updates, or something-else UI related), or when uploading files, etc.
PHP's library is pretty huge and provides a ton of convenient functions that can greatly shorten various tasks. You could just search every time you try to do something, but beyond wasting time you might not find anything that matches your particular search.
Closes the file associated with the stream and disassociates it. All internal buffers associated with the stream are disassociated from it and flushed: the content of any unwritten output buffer is written and the content of any unread input buffer is discarded.
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