--- a/src/ucx/buffer.c Sat Nov 29 19:03:52 2025 +0100
+++ b/src/ucx/buffer.c Sun Nov 30 18:25:55 2025 +0100
@@ -35,7 +35,7 @@
#ifdef _WIN32
#include <Windows.h>
#include <sysinfoapi.h>
-static unsigned long system_page_size() {
+static unsigned long system_page_size(void) {
static unsigned long ps = 0;
if (ps == 0) {
SYSTEM_INFO sysinfo;
@@ -44,16 +44,27 @@
}
return ps;
}
-#define SYSTEM_PAGE_SIZE system_page_size()
#else
#include <unistd.h>
-#define SYSTEM_PAGE_SIZE sysconf(_SC_PAGESIZE)
+static unsigned long system_page_size(void) {
+ static unsigned long ps = 0;
+ if (ps == 0) {
+ long sc = sysconf(_SC_PAGESIZE);
+ if (sc < 0) {
+ // fallback for systems which do not report a value here
+ ps = 4096; // LCOV_EXCL_LINE
+ } else {
+ ps = (unsigned long) sc;
+ }
+ }
+ return ps;
+}
#endif
static int buffer_copy_on_write(CxBuffer* buffer) {
if (0 == (buffer->flags & CX_BUFFER_COPY_ON_WRITE)) return 0;
void *newspace = cxMalloc(buffer->allocator, buffer->capacity);
- if (NULL == newspace) return -1;
+ if (NULL == newspace) return -1; // LCOV_EXCL_LINE
memcpy(newspace, buffer->space, buffer->size);
buffer->space = newspace;
buffer->flags &= ~CX_BUFFER_COPY_ON_WRITE;
@@ -78,9 +89,7 @@
buffer->flags = flags;
if (!space) {
buffer->bytes = cxMalloc(allocator, capacity);
- if (buffer->bytes == NULL) {
- return -1; // LCOV_EXCL_LINE
- }
+ if (buffer->bytes == NULL) return -1; // LCOV_EXCL_LINE
buffer->flags |= CX_BUFFER_FREE_CONTENTS;
} else {
buffer->bytes = space;
@@ -122,7 +131,7 @@
allocator = cxDefaultAllocator;
}
CxBuffer *buf = cxMalloc(allocator, sizeof(CxBuffer));
- if (buf == NULL) return NULL;
+ if (buf == NULL) return NULL; // LCOV_EXCL_LINE
if (0 == cxBufferInit(buf, space, capacity, allocator, flags)) {
return buf;
} else {
@@ -183,6 +192,35 @@
}
+size_t cxBufferPop(CxBuffer *buffer, size_t size, size_t nitems) {
+ size_t len;
+ if (cx_szmul(size, nitems, &len)) {
+ // LCOV_EXCL_START
+ errno = EOVERFLOW;
+ return 0;
+ // LCOV_EXCL_STOP
+ }
+ if (len == 0) return 0;
+ if (len > buffer->size) {
+ if (size == 1) {
+ // simple case: everything can be discarded
+ len = buffer->size;
+ } else {
+ // complicated case: misaligned bytes must stay
+ size_t misalignment = buffer->size % size;
+ len = buffer->size - misalignment;
+ }
+ }
+ buffer->size -= len;
+
+ // adjust position, if required
+ if (buffer->pos > buffer->size) {
+ buffer->pos = buffer->size;
+ }
+
+ return len / size;
+}
+
void cxBufferClear(CxBuffer *buffer) {
if (0 == (buffer->flags & CX_BUFFER_COPY_ON_WRITE)) {
memset(buffer->bytes, 0, buffer->size);
@@ -200,36 +238,10 @@
return buffer->pos >= buffer->size;
}
-int cxBufferMinimumCapacity(
- CxBuffer *buffer,
- size_t newcap
-) {
+int cxBufferReserve(CxBuffer *buffer, size_t newcap) {
if (newcap <= buffer->capacity) {
return 0;
}
-
- unsigned long pagesize = SYSTEM_PAGE_SIZE;
- // if page size is larger than 64 KB - for some reason - truncate to 64 KB
- if (pagesize > 65536) pagesize = 65536;
- if (newcap < pagesize) {
- // when smaller as one page, map to the next power of two
- newcap--;
- newcap |= newcap >> 1;
- newcap |= newcap >> 2;
- newcap |= newcap >> 4;
- // last operation only needed for pages larger 4096 bytes
- // but if/else would be more expensive than just doing this
- newcap |= newcap >> 8;
- newcap++;
- } else {
- // otherwise, map to a multiple of the page size
- newcap -= newcap % pagesize;
- newcap += pagesize;
- // note: if newcap is already page aligned,
- // this gives a full additional page (which is good)
- }
-
-
const int force_copy_flags = CX_BUFFER_COPY_ON_WRITE | CX_BUFFER_COPY_ON_EXTEND;
if (buffer->flags & force_copy_flags) {
void *newspace = cxMalloc(buffer->allocator, newcap);
@@ -249,6 +261,38 @@
}
}
+static size_t cx_buffer_calculate_minimum_capacity(size_t mincap) {
+ unsigned long pagesize = system_page_size();
+ // if page size is larger than 64 KB - for some reason - truncate to 64 KB
+ if (pagesize > 65536) pagesize = 65536;
+ if (mincap < pagesize) {
+ // when smaller as one page, map to the next power of two
+ mincap--;
+ mincap |= mincap >> 1;
+ mincap |= mincap >> 2;
+ mincap |= mincap >> 4;
+ // last operation only needed for pages larger 4096 bytes
+ // but if/else would be more expensive than just doing this
+ mincap |= mincap >> 8;
+ mincap++;
+ } else {
+ // otherwise, map to a multiple of the page size
+ mincap -= mincap % pagesize;
+ mincap += pagesize;
+ // note: if newcap is already page aligned,
+ // this gives a full additional page (which is good)
+ }
+ return mincap;
+}
+
+int cxBufferMinimumCapacity(CxBuffer *buffer, size_t newcap) {
+ if (newcap <= buffer->capacity) {
+ return 0;
+ }
+ newcap = cx_buffer_calculate_minimum_capacity(newcap);
+ return cxBufferReserve(buffer, newcap);
+}
+
void cxBufferShrink(
CxBuffer *buffer,
size_t reserve
@@ -351,8 +395,17 @@
bool perform_flush = false;
if (required > buffer->capacity) {
if (buffer->flags & CX_BUFFER_AUTO_EXTEND) {
- if (buffer->flush != NULL && required > buffer->flush->threshold) {
- perform_flush = true;
+ if (buffer->flush != NULL) {
+ size_t newcap = cx_buffer_calculate_minimum_capacity(required);
+ if (newcap > buffer->flush->threshold) {
+ newcap = buffer->flush->threshold;
+ }
+ if (cxBufferReserve(buffer, newcap)) {
+ return total_flushed; // LCOV_EXCL_LINE
+ }
+ if (required > newcap) {
+ perform_flush = true;
+ }
} else {
if (cxBufferMinimumCapacity(buffer, required)) {
return total_flushed; // LCOV_EXCL_LINE