comparison: src/buffer.c
src/buffer.c
- changeset 1291
- 5942859fd76c
- parent 1290
- 4ac889e14211
- child 1292
- 1e7ee17777f4
equal
deleted
inserted
replaced
| 1290:4ac889e14211 | 1291:5942859fd76c |
|---|---|
| 27 */ | 27 */ |
| 28 | 28 |
| 29 #include "cx/buffer.h" | 29 #include "cx/buffer.h" |
| 30 | 30 |
| 31 #include <stdio.h> | 31 #include <stdio.h> |
| 32 #include <unistd.h> | |
| 32 #include <string.h> | 33 #include <string.h> |
| 33 #include <errno.h> | 34 #include <errno.h> |
| 34 | 35 |
| 35 static int buffer_copy_on_write(CxBuffer* buffer) { | 36 static int buffer_copy_on_write(CxBuffer* buffer) { |
| 36 if (0 == (buffer->flags & CX_BUFFER_COPY_ON_WRITE)) return 0; | 37 if (0 == (buffer->flags & CX_BUFFER_COPY_ON_WRITE)) return 0; |
| 187 size_t newcap | 188 size_t newcap |
| 188 ) { | 189 ) { |
| 189 if (newcap <= buffer->capacity) { | 190 if (newcap <= buffer->capacity) { |
| 190 return 0; | 191 return 0; |
| 191 } | 192 } |
| 193 | |
| 194 unsigned long pagesize = sysconf(_SC_PAGESIZE); | |
| 195 // if page size is larger than 64 KB - for some reason - truncate to 64 KB | |
| 196 if (pagesize > 65536) pagesize = 65536; | |
| 197 if (newcap < pagesize) { | |
| 198 // when smaller as one page, map to the next power of two | |
| 199 newcap--; | |
| 200 newcap |= newcap >> 1; | |
| 201 newcap |= newcap >> 2; | |
| 202 newcap |= newcap >> 4; | |
| 203 // last operation only needed for pages larger 4096 bytes | |
| 204 // but if/else would be more expensive than just doing this | |
| 205 newcap |= newcap >> 8; | |
| 206 newcap++; | |
| 207 } else { | |
| 208 // otherwise, map to a multiple of the page size | |
| 209 newcap -= newcap % pagesize; | |
| 210 newcap += pagesize; | |
| 211 // note: if newcap is already page aligned, | |
| 212 // this gives a full additional page (which is good) | |
| 213 } | |
| 214 | |
| 192 | 215 |
| 193 const int force_copy_flags = CX_BUFFER_COPY_ON_WRITE | CX_BUFFER_COPY_ON_EXTEND; | 216 const int force_copy_flags = CX_BUFFER_COPY_ON_WRITE | CX_BUFFER_COPY_ON_EXTEND; |
| 194 if (buffer->flags & force_copy_flags) { | 217 if (buffer->flags & force_copy_flags) { |
| 195 void *newspace = cxMalloc(buffer->allocator, newcap); | 218 void *newspace = cxMalloc(buffer->allocator, newcap); |
| 196 if (NULL == newspace) return -1; | 219 if (NULL == newspace) return -1; |
