5.6 I/O Function Types

These function types define the low-level interface that serd uses to read and write input.

They are deliberately compatible with the standard C functions for reading and writing from files.

typedef size_t (*SerdReadFunc)(void *buf, size_t size, size_t nmemb, void *stream)

Function for reading input bytes from a stream.

This has identical semantics to fread, but may set errno for more informative error reporting than supported by SerdErrorFunc.

Parameters

  • buf – Output buffer.

  • size – Size of a single element of data in bytes (always 1).

  • nmemb – Number of elements to read.

  • stream – Stream to read from (FILE* for fread).

Returns

Number of elements (bytes) read, which is short on error.

typedef size_t (*SerdWriteFunc)(const void *buf, size_t size, size_t nmemb, void *stream)

Function for writing output bytes to a stream.

This has identical semantics to fwrite, but may set errno for more informative error reporting than supported by SerdErrorFunc.

Parameters

  • buf – Input buffer.

  • size – Size of a single element of data in bytes (always 1).

  • nmemb – Number of elements to read.

  • stream – Stream to write to (FILE* for fread).

Returns

Number of elements (bytes) written, which is short on error.

typedef int (*SerdErrorFunc)(void *stream)

Function for detecting I/O stream errors.

This has identical semantics to ferror.

Returns

Non-zero if stream has encountered an error.

typedef int (*SerdCloseFunc)(void *stream)

Function for closing an I/O stream.

This has identical semantics to fclose. Note that when writing, this may flush the stream which can cause errors, including errors caused by previous writes that appeared successful at the time. Therefore it is necessary to check the return value of this function to properly detect write errors.

Returns

Non-zero if stream has encountered an error.