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