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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Copyright (c) 2015 Google, Inc
* Written by Simon Glass <sjg@chromium.org>
*
* Copyright (c) 1992 Simon Glass
*/
#ifndef _MEMBUFF_H
#define _MEMBUFF_H
/**
* @struct membuff: holds the state of a membuff - it is used for input and
* output buffers. The buffer extends from @start to (@start + @size - 1).
* Data in the buffer extends from @tail to @head: it is written in at
* @head and read out from @tail. The membuff is empty when @head == @tail
* and full when adding another character would make @head == @tail. We
* therefore waste one character in the membuff to avoid having an extra flag
* to determine whether (when @head == @tail) the membuff is empty or full.
*
* xxxxxx data
* ...... empty
*
* .............xxxxxxxxxxxxxxxx.........................
* ^ ^
* tail head
*
* xxxxxxxxxxxxx................xxxxxxxxxxxxxxxxxxxxxxxxx
* ^ ^
* head tail
*/
struct membuff {
char *start; /** the start of the buffer */
char *end; /** the end of the buffer (start + length) */
char *head; /** current buffer head */
char *tail; /** current buffer tail */
};
/**
* membuff_purge() - reset a membuff to the empty state
*
* Initialise head and tail pointers so that the membuff becomes empty.
*
* @mb: membuff to purge
*/
void membuff_purge(struct membuff *mb);
/**
* membuff_putraw() - find out where bytes can be written
*
* Work out where in the membuff some data could be written. Return a pointer
* to the address and the number of bytes which can be written there. If
* @update is true, the caller must then write the data immediately, since
* the membuff is updated as if the write has been done,
*
* Note that because the spare space in a membuff may not be contiguous, this
* function may not return @maxlen even if there is enough space in the
* membuff. However, by calling this function twice (with @update == true),
* you will get access to all the spare space.
*
* @mb: membuff to adjust
* @maxlen: the number of bytes we want to write
* @update: true to update the membuff as if the write happened, false to not
* @data: the address data can be written to
* @return number of bytes which can be written
*/
int membuff_putraw(struct membuff *mb, int maxlen, bool update, char **data);
/**
* membuff_getraw() - find and return a pointer to available bytes
*
* Returns a pointer to any valid input data in the given membuff and
* optionally marks it as read. Note that not all input data may not be
* returned, since data is not necessarily contiguous in the membuff. However,
* if you call this function twice (with @update == true) you are guaranteed
* to get all available data, in at most two installments.
*
* @mb: membuff to adjust
* @maxlen: maximum number of bytes to get
* @update: true to update the membuff as if the bytes have been read (use
* false to check bytes without reading them)
* @data: returns address of data in input membuff
* @return the number of bytes available at *@data
*/
int membuff_getraw(struct membuff *mb, int maxlen, bool update, char **data);
/**
* membuff_putbyte() - Writes a byte to a membuff
*
* @mb: membuff to adjust
* @ch: byte to write
* @return true on success, false if membuff is full
*/
bool membuff_putbyte(struct membuff *mb, int ch);
/**
* @mb: membuff to adjust
* membuff_getbyte() - Read a byte from the membuff
* @return the byte read, or -1 if the membuff is empty
*/
int membuff_getbyte(struct membuff *mb);
/**
* membuff_peekbyte() - check the next available byte
*
* Return the next byte which membuff_getbyte() would return, without
* removing it from the membuff.
*
* @mb: membuff to adjust
* @return the byte peeked, or -1 if the membuff is empty
*/
int membuff_peekbyte(struct membuff *mb);
/**
* membuff_get() - get data from a membuff
*
* Copies any available data (up to @maxlen bytes) to @buff and removes it
* from the membuff.
*
* @mb: membuff to adjust
* @Buff: address of membuff to transfer bytes to
* @maxlen: maximum number of bytes to read
* @return the number of bytes read
*/
int membuff_get(struct membuff *mb, char *buff, int maxlen);
/**
* membuff_put() - write data to a membuff
*
* Writes some data to a membuff. Returns the number of bytes added. If this
* is less than @lnehgt, then the membuff got full
*
* @mb: membuff to adjust
* @data: the data to write
* @length: number of bytes to write from 'data'
* @return the number of bytes added
*/
int membuff_put(struct membuff *mb, const char *buff, int length);
/**
* membuff_isempty() - check if a membuff is empty
*
* @mb: membuff to check
* @return true if empty, else false
*/
bool membuff_isempty(struct membuff *mb);
/**
* membuff_avail() - check available data in a membuff
*
* @mb: membuff to check
* @return number of bytes of data available
*/
int membuff_avail(struct membuff *mb);
/**
* membuff_size() - get the size of a membuff
*
* Note that a membuff can only old data up to one byte less than its size.
*
* @mb: membuff to check
* @return total size
*/
int membuff_size(struct membuff *mb);
/**
* membuff_makecontig() - adjust all membuff data to be contiguous
*
* This places all data in a membuff into a single contiguous lump, if
* possible
*
* @mb: membuff to adjust
* @return true on success
*/
bool membuff_makecontig(struct membuff *mb);
/**
* membuff_free() - find the number of bytes that can be written to a membuff
*
* @mb: membuff to check
* @return returns the number of bytes free in a membuff
*/
int membuff_free(struct membuff *mb);
/**
* membuff_readline() - read a line of text from a membuff
*
* Reads a line of text of up to 'maxlen' characters from a membuff and puts
* it in @str. Any character less than @minch is assumed to be the end of
* line character
*
* @mb: membuff to adjust
* @str: Place to put the line
* @maxlen: Maximum line length (excluding terminator)
* @return number of bytes read (including terminator) if a line has been
* read, 0 if nothing was there
*/
int membuff_readline(struct membuff *mb, char *str, int maxlen, int minch);
/**
* membuff_extend_by() - expand a membuff
*
* Extends a membuff by the given number of bytes
*
* @mb: membuff to adjust
* @by: Number of bytes to increase the size by
* @max: Maximum size to allow
* @return 0 if the expand succeeded, -ENOMEM if not enough memory, -E2BIG
* if the the size would exceed @max
*/
int membuff_extend_by(struct membuff *mb, int by, int max);
/**
* membuff_init() - set up a new membuff using an existing membuff
*
* @mb: membuff to set up
* @buff: Address of buffer
* @size: Size of buffer
*/
void membuff_init(struct membuff *mb, char *buff, int size);
/**
* membuff_uninit() - clear a membuff so it can no longer be used
*
* @mb: membuff to uninit
*/
void membuff_uninit(struct membuff *mb);
/**
* membuff_new() - create a new membuff
*
* @mb: membuff to init
* @size: size of membuff to create
* @return 0 if OK, -ENOMEM if out of memory
*/
int membuff_new(struct membuff *mb, int size);
/**
* membuff_dispose() - free memory allocated to a membuff and uninit it
*
* @mb: membuff to dispose
*/
void membuff_dispose(struct membuff *mb);
#endif