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Optimize small reads in IoRead.

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Instead of using memmove() to manage the internal output buffer for every small read, track the current buffer position and only move data when the small read cannot be satisfied and more data is needed.
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David Steele 2020-10-08 16:09:38 -04:00 committed by GitHub
parent e0f09687e4
commit 401e4f1df4
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 44 additions and 18 deletions
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9
doc/xml/release.xml
View File

@ -36,6 +36,15 @@
<p>Add option groups.</p>
</release-item>
<release-item>
<release-item-contributor-list>
<release-item-reviewer id="stephen.frost"/>
<release-item-reviewer id="cynthia.shang"/>
</release-item-contributor-list>
<p>Optimize small reads in <code>IoRead</code>.</p>
</release-item>
</release-development-list>
</release-core-list>
</release>

53
src/common/io/read.c
View File

@ -22,7 +22,8 @@ struct IoRead
IoReadInterface interface; // Driver interface
IoFilterGroup *filterGroup; // IO filters
Buffer *input; // Input buffer
Buffer *output; // Output buffer (holds extra data from line read)
Buffer *output; // Internal output buffer (extra output from buffered reads)
size_t outputPos; // Current position in the internal output buffer
bool eofAll; // Is the read done (read and filters complete)?
@ -191,18 +192,18 @@ ioRead(IoRead *this, Buffer *buffer)
// Store size of remaining portion of buffer to calculate total read at the end
size_t outputRemains = bufRemains(buffer);
// Use any data in the output buffer left over from a line read
if (this->output != NULL && bufUsed(this->output) > 0 && bufRemains(buffer) > 0)
// Copy any data in the internal output buffer
if (this->output != NULL && bufUsed(this->output) - this->outputPos > 0 && bufRemains(buffer) > 0)
{
// Internal output buffer remains taking into account the position
size_t outputInternalRemains = bufUsed(this->output) - this->outputPos;
// Determine how much data should be copied
size_t size = bufUsed(this->output) > bufRemains(buffer) ? bufRemains(buffer) : bufUsed(this->output);
size_t size = outputInternalRemains > bufRemains(buffer) ? bufRemains(buffer) : outputInternalRemains;
// Copy data to the user buffer
bufCatSub(buffer, this->output, 0, size);
// Remove copied data from the output buffer
memmove(bufPtr(this->output), bufPtr(this->output) + size, bufUsed(this->output) - size);
bufUsedSet(this->output, bufUsed(this->output) - size);
// Copy data to the output buffer
bufCatSub(buffer, this->output, this->outputPos, size);
this->outputPos += size;
}
// Read data
@ -241,29 +242,45 @@ ioReadLineParam(IoRead *this, bool allowEof)
do
{
if (bufUsed(this->output) > 0)
// Internal output buffer remains taking into account the position
size_t outputInternalRemains = bufUsed(this->output) - this->outputPos;
if (outputInternalRemains > 0)
{
// Internal output buffer pointer taking into account the position
char *outputPtr = (char *)bufPtr(this->output) + this->outputPos;
// Search for a linefeed in the buffer
char *linefeed = memchr(bufPtr(this->output), '\n', bufUsed(this->output));
char *linefeed = memchr(outputPtr, '\n', outputInternalRemains);
// A linefeed was found so get the string
if (linefeed != NULL)
{
// Get the string size
size_t size = (size_t)(linefeed - (char *)bufPtr(this->output) + 1);
size_t size = (size_t)(linefeed - outputPtr);
// Create the string
result = strNewN((char *)bufPtr(this->output), size - 1);
// Remove string from the output buffer
memmove(bufPtr(this->output), bufPtr(this->output) + size, bufUsed(this->output) - size);
bufUsedSet(this->output, bufUsed(this->output) - size);
result = strNewN(outputPtr, size);
this->outputPos += size + 1;
}
}
// Read data if no linefeed was found in the existing buffer
if (result == NULL)
{
// If there is remaining data left in the internal output buffer then trim off the used data
if (outputInternalRemains > 0)
{
memmove(
bufPtr(this->output), bufPtr(this->output) + (bufUsed(this->output) - outputInternalRemains),
outputInternalRemains);
}
// Set used bytes and reset position
bufUsedSet(this->output, outputInternalRemains);
this->outputPos = 0;
// If the buffer is full then the linefeed (if it exists) is outside the buffer
if (bufFull(this->output))
THROW_FMT(FileReadError, "unable to find line in %zu byte buffer", bufSize(this->output));