Cytoplasm/src/include/Io.h

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/*
* Copyright (C) 2022-2023 Jordan Bancino <@jordan:bancino.net>
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef CYTOPLASM_IO_H
#define CYTOPLASM_IO_H
/***
* @Nm Io
* @Nd Source/sink-agnostic I/O for implementing custom streams.
* @Dd April 29 2023
* @Xr Stream Tls
*
* Many systems provide platform-specific means of implementing custom
* streams using file pointers. However, POSIX does not define a way
* of programmatically creating custom streams.
* .Nm
* therefore fills this gap in POSIX by mimicking all of the
* functionality of these platform-specific functions, but in pure
* POSIX C. It defines a number of callback funtions to be executed
* in place of the standard POSIX I/O functions, which are used to
* implement arbitrary streams that may not be to a file or socket.
* Additionally, streams can now be pipelined; the sink of one stream
* may be the source of another lower-level stream. Additionally, all
* streams, regardless of their source or sink, share the same API, so
* streams can be handled in a much more generic manner. This allows
* the HTTP client and server libraries to seemlessly support TLS and
* plain connections without having to handle each separately.
* .Pp
* .Nm
* was heavily inspired by GNU's
* .Fn fopencookie
* and BSD's
* .Fn funopen .
* It aims to combine the best of both of these functions into a single
* API that is intuitive and easy to use.
*/
#include <stdio.h>
#include <stdarg.h>
#include <unistd.h>
#include <sys/types.h>
#ifndef IO_BUFFER
#define IO_BUFFER 4096
#endif
/**
* An opaque structure analogous to a POSIX file descriptor.
*/
typedef struct Io Io;
/**
* Read input from the source of a stream. This function should
* attempt to read the specified number of bytes of data from the
* given cookie into the given buffer. It should behave identically
* to the POSIX
* .Xr read 2
* system call, except instead of using an integer descriptor as the
* first parameter, a pointer to an implementation-defined cookie
* stores any information the function needs to read from the source.
*/
typedef ssize_t (IoReadFunc) (void *, void *, size_t);
/**
* Write output to a sink. This function should attempt to write the
* specified number of bytes of data from the given buffer into the
* stream described by the given cookie. It should behave identically
* to the POSIX
* .Xr write 2
* system call, except instead of using an integer descriptor as the
* first parameter, a pointer to an implementation-defined cookie
* stores any information the function needs to write to the sink.
*/
typedef ssize_t (IoWriteFunc) (void *, void *, size_t);
/**
* Repositions the offset of the stream described by the specified
* cookie. This function should behave identically to the POSIX
* .Xr lseek 2
* system call, except instead of using an integer descriptor as the
* first parameter, a pointer to an implementation-defined cookie
* stores any information the function needs to seek the stream.
*/
typedef off_t (IoSeekFunc) (void *, off_t, int);
/**
* Close the given stream, making future reads or writes result in
* undefined behavior. This function should also free all memory
* associated with the cookie. It should behave identically to the
* .Xr close 2
* system call, except instead of using an integer descriptor for the
* parameter, a pointer to an implementation-defined cookie stores any
* information the function needs to close the stream.
*/
typedef int (IoCloseFunc) (void *);
/**
* A simple mechanism for grouping together a set of stream functions,
* to be passed to
* .Fn IoCreate .
*/
typedef struct IoFunctions
{
IoReadFunc *read;
IoWriteFunc *write;
IoSeekFunc *seek;
IoCloseFunc *close;
} IoFunctions;
/**
* Create a new stream using the specified cookie and the specified
* I/O functions.
*/
extern Io * IoCreate(void *, IoFunctions);
/**
* Read the specified number of bytes from the specified stream into
* the specified buffer. This calls the stream's underlying IoReadFunc,
* which should behave identically to the POSIX
* .Xr read 2
* system call.
*/
extern ssize_t IoRead(Io *, void *, size_t);
/**
* Write the specified number of bytes from the specified stream into
* the specified buffer. This calls the stream's underlying
* IoWriteFunc, which should behave identically to the POSIX
* .Xr write 2
* system call.
*/
extern ssize_t IoWrite(Io *, void *, size_t);
/**
* Seek the specified stream using the specified offset and whence
* value. This calls the stream's underlying IoSeekFunc, which should
* behave identically to the POSIX
* .Xr lseek 2
* system call.
*/
extern off_t IoSeek(Io *, off_t, int);
/**
* Close the specified stream. This calls the stream's underlying
* IoCloseFunc, which should behave identically to the POSIX
* .Xr close 2
* system call.
*/
extern int IoClose(Io *);
/**
* Print a formatted string to the given stream. This is a
* re-implementation of the standard library function
* .Xr vfprintf 3 ,
* and behaves identically.
*/
extern int IoVprintf(Io *, const char *, va_list);
/**
* Print a formatted string to the given stream. This is a
* re-implementation of the standard library function
* .Xr fprintf 3 ,
* and behaves identically.
*/
extern int IoPrintf(Io *, const char *,...);
/**
* Read all the bytes from the first stream and write them to the
* second stream. Neither stream is closed upon the completion of this
* function. This can be used for quick and convenient buffered
* copying of data from one stream into another.
*/
extern ssize_t IoCopy(Io *, Io *);
/**
* Wrap a POSIX file descriptor to take advantage of this API. The
* common use case for this function is when a regular file descriptor
* needs to be accessed by an application that uses this API to also
* access non-POSIX streams.
*/
extern Io * IoFd(int);
/**
* Open or create a file for reading or writing. The specified file
* name is opened for reading or writing as specified by the given
* flags and mode. This function is a simple convenience wrapper around
* the POSIX
* .Xr open 2
* system call that passes the opened file descriptor into
* .Fn IoFd .
*/
extern Io * IoOpen(const char *, int, mode_t);
/**
* Wrap a standard C file pointer to take advantage of this API. The
* common use case for this function is when a regular C file pointer
* needs to be accessed by an application that uses this API to also
* access custom streams.
*/
extern Io * IoFile(FILE *);
#endif /* CYTOPLASM_IO_H */