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Add a circular memory buffer implementation
This will be used to support console recording. It provides for a circular buffer which can be written at the head and read from the tail. It supports avoiding data copying by providing raw access to the data. Signed-off-by: Simon Glass <sjg@chromium.org>
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Simon Glass
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3 changed files with 637 additions and 0 deletions
390
lib/membuff.c
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390
lib/membuff.c
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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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* SPDX-License-Identifier: GPL-2.0+
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*/
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#include <common.h>
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#include <errno.h>
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#include <malloc.h>
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#include "membuff.h"
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void membuff_purge(struct membuff *mb)
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{
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/* set mb->head and mb->tail so the buffers look empty */
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mb->head = mb->start;
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mb->tail = mb->start;
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}
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static int membuff_putrawflex(struct membuff *mb, int maxlen, bool update,
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char ***data, int *offsetp)
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{
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int len;
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/* always write to 'mb->head' */
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assert(data && offsetp);
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*data = &mb->start;
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*offsetp = mb->head - mb->start;
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/* if there is no buffer, we can do nothing */
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if (!mb->start)
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return 0;
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/*
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* if head is ahead of tail, we can write from head until the end of
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* the buffer
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*/
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if (mb->head >= mb->tail) {
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/* work out how many bytes can fit here */
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len = mb->end - mb->head - 1;
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if (maxlen >= 0 && len > maxlen)
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len = maxlen;
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/* update the head pointer to mark these bytes as written */
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if (update)
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mb->head += len;
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/*
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* if the tail isn't at start of the buffer, then we can
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* write one more byte right at the end
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*/
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if ((maxlen < 0 || len < maxlen) && mb->tail != mb->start) {
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len++;
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if (update)
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mb->head = mb->start;
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}
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/* otherwise now we can write until head almost reaches tail */
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} else {
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/* work out how many bytes can fit here */
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len = mb->tail - mb->head - 1;
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if (maxlen >= 0 && len > maxlen)
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len = maxlen;
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/* update the head pointer to mark these bytes as written */
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if (update)
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mb->head += len;
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}
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/* return the number of bytes which can be/must be written */
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return len;
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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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char **datap;
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int offset;
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int size;
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size = membuff_putrawflex(mb, maxlen, update, &datap, &offset);
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*data = *datap + offset;
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return size;
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}
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bool membuff_putbyte(struct membuff *mb, int ch)
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{
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char *data;
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if (membuff_putraw(mb, 1, true, &data) != 1)
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return false;
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*data = ch;
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return true;
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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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int len;
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/* assume for now there is no data to get */
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len = 0;
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/*
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* in this case head is ahead of tail, so we must return data between
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*'tail' and 'head'
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*/
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if (mb->head > mb->tail) {
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/* work out the amount of data */
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*data = mb->tail;
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len = mb->head - mb->tail;
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/* check it isn't too much */
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if (maxlen >= 0 && len > maxlen)
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len = maxlen;
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/* & mark it as read from the buffer */
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if (update)
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mb->tail += len;
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}
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/*
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* if head is before tail, then we have data between 'tail' and 'end'
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* and some more data between 'start' and 'head'(which we can't
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* return this time
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*/
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else if (mb->head < mb->tail) {
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/* work out the amount of data */
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*data = mb->tail;
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len = mb->end - mb->tail;
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if (maxlen >= 0 && len > maxlen)
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len = maxlen;
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if (update) {
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mb->tail += len;
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if (mb->tail == mb->end)
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mb->tail = mb->start;
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}
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}
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debug("getraw: maxlen=%d, update=%d, head=%d, tail=%d, data=%d, len=%d",
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maxlen, update, (int)(mb->head - mb->start),
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(int)(mb->tail - mb->start), (int)(*data - mb->start), len);
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/* return the number of bytes we found */
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return len;
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}
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int membuff_getbyte(struct membuff *mb)
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{
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char *data = 0;
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return membuff_getraw(mb, 1, true, &data) != 1 ? -1 : *(uint8_t *)data;
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}
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int membuff_peekbyte(struct membuff *mb)
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{
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char *data = 0;
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return membuff_getraw(mb, 1, false, &data) != 1 ? -1 : *(uint8_t *)data;
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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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char *data = 0, *buffptr = buff;
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int len = 1, i;
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/*
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* do this in up to two lots(see GetRaw for why) stopping when there
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* is no more data
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*/
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for (i = 0; len && i < 2; i++) {
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/* get a pointer to the data available */
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len = membuff_getraw(mb, maxlen, true, &data);
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/* copy it into the buffer */
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memcpy(buffptr, data, len);
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buffptr += len;
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maxlen -= len;
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}
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/* return the number of bytes read */
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return buffptr - buff;
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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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char *data;
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int towrite, i, written;
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for (i = written = 0; i < 2; i++) {
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/* ask where some data can be written */
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towrite = membuff_putraw(mb, length, true, &data);
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/* and write it, updating the bytes length */
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memcpy(data, buff, towrite);
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written += towrite;
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buff += towrite;
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length -= towrite;
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}
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/* return the number of bytes written */
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return written;
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}
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bool membuff_isempty(struct membuff *mb)
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{
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return mb->head == mb->tail;
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}
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int membuff_avail(struct membuff *mb)
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{
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struct membuff copy;
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int i, avail;
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char *data = 0;
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/* make a copy of this buffer's control data */
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copy = *mb;
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/* now read everything out of the copied buffer */
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for (i = avail = 0; i < 2; i++)
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avail += membuff_getraw(©, -1, true, &data);
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/* and return how much we read */
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return avail;
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}
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int membuff_size(struct membuff *mb)
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{
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return mb->end - mb->start;
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}
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bool membuff_makecontig(struct membuff *mb)
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{
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int topsize, botsize;
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debug("makecontig: head=%d, tail=%d, size=%d",
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(int)(mb->head - mb->start), (int)(mb->tail - mb->start),
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(int)(mb->end - mb->start));
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/*
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* first we move anything at the start of the buffer into the correct
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* place some way along
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*/
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if (mb->tail > mb->head) {
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/*
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* the data is split into two parts, from 0 to ->head and
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* from ->tail to ->end. We move the stuff from 0 to ->head
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* up to make space for the other data before it
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*/
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topsize = mb->end - mb->tail;
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botsize = mb->head - mb->start;
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/*
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* must move data at bottom up by 'topsize' bytes - check if
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* there's room
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*/
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if (mb->head + topsize >= mb->tail)
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return false;
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memmove(mb->start + topsize, mb->start, botsize);
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debug(" - memmove(%d, %d, %d)", topsize, 0, botsize);
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/* nothing at the start, so skip that step */
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} else {
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topsize = mb->head - mb->tail;
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botsize = 0;
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}
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/* now move data at top down to the bottom */
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memcpy(mb->start, mb->tail, topsize);
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debug(" - memcpy(%d, %d, %d)", 0, (int)(mb->tail - mb->start), topsize);
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/* adjust pointers */
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mb->tail = mb->start;
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mb->head = mb->start + topsize + botsize;
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debug(" - head=%d, tail=%d", (int)(mb->head - mb->start),
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(int)(mb->tail - mb->start));
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/* all ok */
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return true;
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}
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int membuff_free(struct membuff *mb)
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{
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return mb->end == mb->start ? 0 :
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(mb->end - mb->start) - 1 - membuff_avail(mb);
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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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int len; /* number of bytes read (!= string length) */
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char *s, *end;
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bool ok = false;
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char *orig = str;
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end = mb->head >= mb->tail ? mb->head : mb->end;
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for (len = 0, s = mb->tail; s < end && len < maxlen - 1; str++) {
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*str = *s++;
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len++;
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if (*str == '\n' || *str < minch) {
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ok = true;
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break;
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}
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if (s == end && mb->tail > mb->head) {
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s = mb->start;
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end = mb->head;
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}
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}
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/* couldn't get the whole string */
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if (!ok) {
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if (maxlen)
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*orig = '\0';
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return 0;
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}
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/* terminate the string, update the membuff and return success */
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*str = '\0';
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mb->tail = s == mb->end ? mb->start : s;
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return len;
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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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int oldhead, oldtail;
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int size, orig;
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char *ptr;
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/* double the buffer size until it is big enough */
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assert(by >= 0);
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for (orig = mb->end - mb->start, size = orig; size < orig + by;)
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size *= 2;
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if (max != -1)
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size = min(size, max);
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by = size - orig;
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/* if we're already at maximum, give up */
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if (by <= 0)
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return -E2BIG;
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oldhead = mb->head - mb->start;
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oldtail = mb->tail - mb->start;
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ptr = realloc(mb->start, size);
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if (!ptr)
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return -ENOMEM;
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mb->start = ptr;
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mb->head = mb->start + oldhead;
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mb->tail = mb->start + oldtail;
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if (mb->head < mb->tail) {
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memmove(mb->tail + by, mb->tail, orig - oldtail);
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mb->tail += by;
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}
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mb->end = mb->start + size;
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return 0;
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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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mb->start = buff;
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mb->end = mb->start + size;
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membuff_purge(mb);
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}
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int membuff_new(struct membuff *mb, int size)
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{
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mb->start = malloc(size);
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if (!mb->start)
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return -ENOMEM;
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membuff_init(mb, mb->start, size);
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return 0;
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}
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void membuff_uninit(struct membuff *mb)
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{
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mb->end = NULL;
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mb->start = NULL;
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membuff_purge(mb);
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}
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void membuff_dispose(struct membuff *mb)
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{
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free(&mb->start);
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membuff_uninit(mb);
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}
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