diff options
Diffstat (limited to 'libdimension/canvas.c')
| -rw-r--r-- | libdimension/canvas.c | 32 |
1 files changed, 29 insertions, 3 deletions
diff --git a/libdimension/canvas.c b/libdimension/canvas.c index 49096fc..516c978 100644 --- a/libdimension/canvas.c +++ b/libdimension/canvas.c @@ -19,24 +19,33 @@ *************************************************************************/ #include "dimension.h" -#include <pthread.h> /* Must be first included header */ -#include <stdlib.h> /* For malloc(), free() */ +#include <pthread.h> +#include <stdlib.h> /* For malloc(), free() */ +/* Allocate a new canvas, of width x and height y. If any intermediary step + fails, free all acquired memory to avoid leaks. */ dmnsn_canvas * dmnsn_new_canvas(unsigned int x, unsigned int y) { unsigned int i, j, k, l; + /* Allocate the dmnsn_canvas struct */ dmnsn_canvas *canvas = malloc(sizeof(dmnsn_canvas)); if (canvas) { + /* *canvas exists */ + + /* Set the width and height */ canvas->x = x; canvas->y = y; + + /* Allocate the pixels */ canvas->pixels = malloc(sizeof(dmnsn_color)*x*y); if (!canvas->pixels) { free(canvas); return NULL; } + /* Allocate the rwlocks */ canvas->rwlocks = malloc(sizeof(pthread_rwlock_t)*x*y); if (!canvas->rwlocks) { free(canvas->pixels); @@ -44,6 +53,7 @@ dmnsn_new_canvas(unsigned int x, unsigned int y) return NULL; } + /* Initialize the rwlocks */ for (i = 0; i < x; ++i) { for (j = 0; j < y; ++j) { if (pthread_rwlock_init(&canvas->rwlocks[j*x + i], NULL) != 0) { @@ -53,7 +63,7 @@ dmnsn_new_canvas(unsigned int x, unsigned int y) for (l = 0; l < j; ++l) { for (k = 0; k < x; ++k) { if (pthread_rwlock_destroy(&canvas->rwlocks[l*x + k]) != 0) { - /* Low severity, because leaked memory won't actually hurt us */ + /* Low severity, because leaked locks won't actually hurt us */ dmnsn_error(DMNSN_SEVERITY_LOW, "Leaking rwlocks in failed allocation."); } @@ -79,12 +89,16 @@ dmnsn_new_canvas(unsigned int x, unsigned int y) return canvas; } +/* Delete a dmnsn_canvas allocated with dmnsn_new_canvas */ void dmnsn_delete_canvas(dmnsn_canvas *canvas) { unsigned int i, j; if (canvas) { + /* *canvas exists */ + + /* Destroy the rwlocks */ for (i = 0; i < canvas->x; ++i) { for (j = 0; j < canvas->y; ++j) { if (pthread_rwlock_destroy(&canvas->rwlocks[j*canvas->x + i]) != 0) { @@ -94,12 +108,14 @@ dmnsn_delete_canvas(dmnsn_canvas *canvas) } } + /* Free the locks, pixels, and canvas */ free(canvas->rwlocks); free(canvas->pixels); free(canvas); } } +/* Get a pixel at (x,y) thread-safely, using dmnsn_rdlock_pixel. */ dmnsn_color dmnsn_get_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y) { @@ -110,6 +126,7 @@ dmnsn_get_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y) return color; } +/* Set a pixel at (x,y) thread-safely, using dmnsn_wrlock_pixel. */ void dmnsn_set_pixel(dmnsn_canvas *canvas, unsigned int x, unsigned int y, dmnsn_color color) @@ -119,28 +136,37 @@ dmnsn_set_pixel(dmnsn_canvas *canvas, dmnsn_unlock_pixel(canvas, x, y); } +/* Acquire a read-lock for a pixel */ void dmnsn_rdlock_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y) { if (pthread_rwlock_rdlock(&canvas->rwlocks[y*canvas->x + x]) != 0) { + /* Medium severity, because undefined behaviour is pretty likely if our + reads and writes aren't synced */ dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't acquire read-lock for pixel."); } } +/* Acquire a write-lock for a pixel */ void dmnsn_wrlock_pixel(dmnsn_canvas *canvas, unsigned int x, unsigned int y) { if (pthread_rwlock_wrlock(&canvas->rwlocks[y*canvas->x + x]) != 0) { + /* Medium severity, because undefined behaviour is pretty likely if our + reads and writes aren't synced */ dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't acquire write-lock for pixel."); } } +/* Unlock a pixel */ void dmnsn_unlock_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y) { if (pthread_rwlock_unlock(&canvas->rwlocks[y*canvas->x + x]) != 0) { + /* Medium severity, because if the pixel is locked, we're likely to hang + the next time we try to read or write it */ dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't unlock pixel."); } } |