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/*
Ousía
Copyright (C) 2014 Benjamin Paaßen, Andreas Stöckel
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm>
#include "Buffer.hpp"
namespace ousia {
namespace utils {
/* Class Buffer */
Buffer::Buffer(ReadCallback callback, void *userData)
: callback(callback),
userData(userData),
reachedEnd(false),
startBucket(buckets.end()),
endBucket(buckets.end()),
startOffset(0),
firstDead(0)
{
// Insert a first empty bucket and set the start buffer correctly
nextBucket();
startBucket = buckets.begin();
}
Buffer::Buffer(const std::string &str)
: callback(nullptr),
userData(nullptr),
reachedEnd(true),
startBucket(buckets.end()),
endBucket(buckets.end()),
startOffset(0),
firstDead(0)
{
// Copy the given string into a first buffer and set the start buffer
// correctly
Bucket &bucket = nextBucket();
bucket.resize(str.size());
std::copy(str.begin(), str.end(), bucket.begin());
startBucket = buckets.begin();
}
void Buffer::advance(BucketIterator &it)
{
it++;
if (it == buckets.end()) {
it = buckets.begin();
}
}
void Buffer::advance(BucketList::const_iterator &it) const
{
it++;
if (it == buckets.cend()) {
it = buckets.cbegin();
}
}
Buffer::Bucket &Buffer::nextBucket()
{
// Fetch the minimum bucket index
size_t minBucketIdx = 0;
for (size_t i = 0; i < cursors.size(); i++) {
if (alive[i]) {
minBucketIdx = std::min(minBucketIdx, cursors[i].bucketIdx);
}
}
// If there is space between the current start bucket and the read
// cursor, the start bucket can be safely overridden.
if (minBucketIdx > 0) {
// All cursor bucket indices will be decreased by one
for (size_t i = 0; i < cursors.size(); i++) {
cursors[i].bucketIdx--;
}
// Increment the start offset
startOffset += startBucket->size();
// The old start bucket is the new end bucket
endBucket = startBucket;
// Advance the start bucket, wrap around at the end of the list
advance(startBucket);
} else {
// No free bucket, insert a new one before the start bucket
endBucket = buckets.emplace(startBucket);
}
return *endBucket;
}
Buffer::CursorId Buffer::nextCursor()
{
bool hasCursor = false;
CursorId res = 0;
// Search for the next free cursor starting with minNextCursorId
for (size_t i = firstDead; i < alive.size(); i++) {
if (!alive[i]) {
res = i;
hasCursor = true;
break;
}
}
// Add a new cursor to the cursor list if no cursor is currently free
if (!hasCursor) {
res = cursors.size();
cursors.resize(res + 1);
alive.resize(res + 1);
}
// The next dead cursor is at least the next cursor
firstDead = res + 1;
// Mark the new cursor as alive
alive[res] = true;
return res;
}
void Buffer::stream()
{
// Fetch the bucket into which the data should be inserted, make sure it
// has the correct size
Bucket &tar = nextBucket();
tar.resize(REQUEST_SIZE);
// Read data from the stream into the target buffer
size_t size = callback(tar.data(), REQUEST_SIZE, userData);
// If not enough bytes were returned, we're at the end of the stream
if (size < REQUEST_SIZE) {
tar.resize(size);
reachedEnd = true;
}
}
Buffer::CursorId Buffer::createCursor()
{
CursorId res = nextCursor();
cursors[res].bucket = startBucket;
cursors[res].bucketIdx = 0;
cursors[res].bucketOffs = 0;
return res;
}
Buffer::CursorId Buffer::createCursor(Buffer::CursorId ref)
{
CursorId res = nextCursor();
cursors[res] = cursors[ref];
return res;
}
void Buffer::copyCursor(Buffer::CursorId from, Buffer::CursorId to)
{
cursors[to] = cursors[from];
}
void Buffer::deleteCursor(Buffer::CursorId cursor)
{
alive[cursor] = false;
firstDead = std::min(firstDead, cursor);
}
size_t Buffer::offset(Buffer::CursorId cursor) const
{
const Cursor &c = cursors[cursor];
size_t offs = startOffset + c.bucketOffs;
BucketList::const_iterator it = startBucket;
while (it != c.bucket) {
offs += it->size();
advance(it);
}
return offs;
}
bool Buffer::atEnd(Buffer::CursorId cursor) const
{
const Cursor &c = cursors[cursor];
return reachedEnd &&
(c.bucket == endBucket && c.bucketOffs == endBucket->size());
}
bool Buffer::read(Buffer::CursorId cursor, char &c)
{
Cursor &cur = cursors[cursor];
while (true) {
// Reference at the current bucket
Bucket &bucket = *(cur.bucket);
// If there is still data in the current bucket, return this data
if (cur.bucketOffs < bucket.size()) {
c = bucket[cur.bucketOffs];
cur.bucketOffs++;
return true;
} else if (cur.bucket == endBucket) {
// Return false if the end of the stream has been reached, otherwise
// load new data
if (reachedEnd) {
return false;
}
stream();
}
// Go to the next bucket
cur.bucketIdx++;
cur.bucketOffs = 0;
advance(cur.bucket);
}
}
}
}
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