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Switch string pool code to an insertion sort - provides a modest 25% improvement

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to open speeds on typical files.
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Michael R Sweet 2024-01-27 20:58:50 -05:00
parent b117959725
commit 6c1db141a1
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GPG Key ID: BE67C75EC81F3244
2 changed files with 82 additions and 15 deletions
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1
CHANGES.md
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@ -6,6 +6,7 @@ v1.2.1 (Month DD, YYYY)
-----------------------
- Updated number support to avoid locale issues (Issue #61)
- Optimized string pool code.
v1.2.0 (January 24, 2024)

96
pdfio-string.c
View File

@ -14,7 +14,7 @@
// Local functions...
//
static int compare_strings(char **a, char **b);
static size_t find_string(pdfio_file_t *pdf, const char *s, int *rdiff);
//
@ -385,8 +385,9 @@ pdfioStringCreate(
pdfio_file_t *pdf, // I - PDF file
const char *s) // I - Nul-terminated string
{
char *news; // New string
char **match; // Matching string
char *news; // New string
size_t idx; // Index into strings
int diff; // Different
PDFIO_DEBUG("pdfioStringCreate(pdf=%p, s=\"%s\")\n", pdf, s);
@ -396,8 +397,17 @@ pdfioStringCreate(
return (NULL);
// See if the string has already been added...
if (pdf->num_strings > 0 && (match = (char **)bsearch(&s, pdf->strings, pdf->num_strings, sizeof(char *), (int (*)(const void *, const void *))compare_strings)) != NULL)
return (*match);
if (pdf->num_strings > 0)
{
idx = find_string(pdf, s, &diff);
if (diff == 0)
return (pdf->strings[idx]);
}
else
{
idx = 0;
diff = -1;
}
// Not already added, so add it...
if ((news = strdup(s)) == NULL)
@ -418,11 +428,17 @@ pdfioStringCreate(
pdf->alloc_strings += 128;
}
// TODO: Change to insertion sort as needed...
pdf->strings[pdf->num_strings ++] = news;
// Insert the string...
if (diff > 0)
idx ++;
if (pdf->num_strings > 1)
qsort(pdf->strings, pdf->num_strings, sizeof(char *), (int (*)(const void *, const void *))compare_strings);
PDFIO_DEBUG("pdfioStringCreate: Inserting \"%s\" at %u\n", news, (unsigned)idx);
if (idx < pdf->num_strings)
memmove(pdf->strings + idx + 1, pdf->strings + idx, (pdf->num_strings - idx) * sizeof(char *));
pdf->strings[idx] = news;
pdf->num_strings ++;
PDFIO_DEBUG("pdfioStringCreate: %lu strings\n", (unsigned long)pdf->num_strings);
@ -473,17 +489,67 @@ _pdfioStringIsAllocated(
pdfio_file_t *pdf, // I - PDF file
const char *s) // I - String
{
return (pdf->num_strings > 0 && bsearch(&s, pdf->strings, pdf->num_strings, sizeof(char *), (int (*)(const void *, const void *))compare_strings) != NULL);
int diff; // Difference
if (pdf->num_strings == 0)
return (false);
find_string(pdf, s, &diff);
return (diff == 0);
}
//
// 'compare_strings()' - Compare two strings.
// 'find_string()' - Find an element in the array.
//
static int // O - Result of comparison
compare_strings(char **a, // I - First string
char **b) // I - Second string
static size_t // O - Index of match
find_string(pdfio_file_t *pdf, // I - PDF file
const char *s, // I - String to find
int *rdiff) // O - Difference of match
{
return (strcmp(*a, *b));
size_t left, // Left side of search
right, // Right side of search
current; // Current element
int diff; // Comparison with current element
// Do a binary search for the string...
left = 0;
right = pdf->num_strings - 1;
do
{
current = (left + right) / 2;
diff = strcmp(s, pdf->strings[current]);
if (diff == 0)
break;
else if (diff < 0)
right = current;
else
left = current;
}
while ((right - left) > 1);
if (diff != 0)
{
// Check the last 1 or 2 elements...
if ((diff = strcmp(s, pdf->strings[left])) <= 0)
{
current = left;
}
else
{
diff = strcmp(s, pdf->strings[right]);
current = right;
}
}
// Return the closest string and the difference...
*rdiff = diff;
return (current);
}