Add read-write mutexes to canvas pixels. New error infrastructure.

5 files changed, 210 insertions, 7 deletions

diff --git a/libdimension/Makefile.am b/libdimension/Makefile.am
index 69bcbb3..60c9347 100644
--- a/libdimension/Makefile.am
+++ b/libdimension/Makefile.am
@@ -21,5 +21,6 @@ nobase_include_HEADERS = dimension.h dimension/geometry.h dimension/color.h dime
 
 lib_LTLIBRARIES = libdimension.la
 
-libdimension_la_SOURCES = dimension.h dimension/geometry.h dimension/color.h dimension/canvas.h canvas.c color.c geometry.c
+libdimension_la_SOURCES = dimension.h dimension/geometry.h dimension/color.h dimension/canvas.h canvas.c color.c geometry.c error.c
 libdimension_la_LDFLAGS = -version-info 0:0:0
+libdimension_la_LIBADD  = -lm -lpthread
diff --git a/libdimension/canvas.c b/libdimension/canvas.c
index 21d6d86..e56c391 100644
--- a/libdimension/canvas.c
+++ b/libdimension/canvas.c
@@ -19,34 +19,128 @@
  *************************************************************************/
 
 #include "dimension.h"
-#include <stdlib.h> /* For malloc(), free() */
+#include <pthread.h> /* Must be first included header */
+#include <stdlib.h>  /* For malloc(), free() */
 
 dmnsn_canvas *
 dmnsn_new_canvas(unsigned int x, unsigned int y)
 {
+  unsigned int i, j, k, l;
   dmnsn_canvas *canvas = malloc(sizeof(dmnsn_canvas));
 
   if (canvas) {
     canvas->x = x;
     canvas->y = y;
     canvas->pixels = malloc(sizeof(dmnsn_color)*x*y);
+    if (!canvas->pixels) {
+      free(canvas);
+      return NULL;
+    }
 
-    if (canvas->pixels) {
-      return canvas;
-    } else {
+    canvas->rwlocks = malloc(sizeof(pthread_rwlock_t)*x*y);
+    if (!canvas->rwlocks) {
+      free(canvas->pixels);
       free(canvas);
       return NULL;
     }
-  } else {
-    return NULL;
+
+    for (i = 0; i < x; ++i) {
+      for (j = 0; j < y; ++j) {
+        if (pthread_rwlock_init(&canvas->rwlocks[j*x + i], NULL) != 0) {
+          /* pthread_rwlock_init failed.  Destroy the locks we've already made,
+             free the canvas, and return NULL.  We leak memory if destruction
+             fails (i.e. someone is somehow using an rwlock already). */
+          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 */
+                dmnsn_error(DMNSN_SEVERITY_LOW,
+                            "Leaking rwlocks in failed allocation.");
+              }
+            }
+          }
+
+          for (k = 0; k < i; ++k) {
+            if (pthread_rwlock_destroy(&canvas->rwlocks[j*x + k]) != 0) {
+              dmnsn_error(DMNSN_SEVERITY_LOW,
+                          "Leaking rwlocks in failed allocation.");
+            }
+          }
+
+          free(canvas->rwlocks);
+          free(canvas->pixels);
+          free(canvas);
+          return NULL;
+        }
+      }
+    }
   }
+
+  return canvas;
 }
 
 void
 dmnsn_delete_canvas(dmnsn_canvas *canvas)
 {
+  unsigned int i, j;
+
   if (canvas) {
+    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) {
+              dmnsn_error(DMNSN_SEVERITY_LOW,
+                          "Leaking rwlocks in deallocation.");
+        }
+      }
+    }
+
+    free(canvas->rwlocks);
     free(canvas->pixels);
     free(canvas);
   }
 }
+
+dmnsn_color
+dmnsn_get_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y)
+{
+  dmnsn_color color;
+  dmnsn_rdlock_pixel(canvas, x, y);
+  color = canvas->pixels[y*canvas->x + x];
+  dmnsn_unlock_pixel(canvas, x, y);
+  return color;
+}
+
+void
+dmnsn_set_pixel(dmnsn_canvas *canvas, dmnsn_color color,
+                unsigned int x, unsigned int y)
+{
+  dmnsn_wrlock_pixel(canvas, x, y);
+  canvas->pixels[y*canvas->x + x] = color;
+  dmnsn_unlock_pixel(canvas, x, y);
+}
+
+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) {
+    dmnsn_error(DMNSN_SEVERITY_MEDIUM,
+                "Couldn't acquire read-lock for 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) {
+    dmnsn_error(DMNSN_SEVERITY_MEDIUM,
+                "Couldn't acquire write-lock for 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) {
+    dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't unlock pixel.");
+  }
+}
diff --git a/libdimension/dimension.h b/libdimension/dimension.h
index 558c9ed..fa38629 100644
--- a/libdimension/dimension.h
+++ b/libdimension/dimension.h
@@ -28,6 +28,22 @@
 extern "C" {
 #endif
 
+/* Debug and error handling stuff */
+
+typedef enum {
+  DMNSN_SEVERITY_LOW,    /* Only die on low resilience */
+  DMNSN_SEVERITY_MEDIUM, /* Die on low or medium resilience */
+  DMNSN_SEVERITY_HIGH    /* Always die */
+} dmnsn_severity;
+
+#define dmnsn_error(severity, str) dmnsn_report_error(severity, __func__, str)
+
+void dmnsn_report_error(dmnsn_severity severity,
+                        const char *func, const char *str);
+dmnsn_severity dmnsn_get_resilience();
+void dmnsn_set_resilience(dmnsn_severity resilience);
+
+/* More includes */
 #include <dimension/geometry.h>
 #include <dimension/color.h>
 #include <dimension/canvas.h>
diff --git a/libdimension/dimension/canvas.h b/libdimension/dimension/canvas.h
index 21d56e4..d40ed1d 100644
--- a/libdimension/dimension/canvas.h
+++ b/libdimension/dimension/canvas.h
@@ -25,6 +25,8 @@
 #ifndef DIMENSION_CANVAS_H
 #define DIMENSION_CANVAS_H
 
+#include <pthread.h>
+
 typedef struct {
   unsigned int x, y;
 
@@ -33,9 +35,25 @@ typedef struct {
    * at (a,b) is accessible as pixels[b*x + a].
    */
   dmnsn_color *pixels;
+
+  /* Read-write locks for each pixel */
+  pthread_rwlock_t *rwlocks;
 } dmnsn_canvas;
 
 dmnsn_canvas *dmnsn_new_canvas(unsigned int x, unsigned int y);
 void dmnsn_delete_canvas(dmnsn_canvas *canvas);
 
+/* These handle the rwlocks correctly */
+dmnsn_color dmnsn_get_pixel(const dmnsn_canvas *canvas,
+                            unsigned int x, unsigned int y);
+void dmnsn_set_pixel(dmnsn_canvas *canvas, dmnsn_color color,
+                     unsigned int x, unsigned int y);
+
+/* Manual locking */
+void dmnsn_rdlock_pixel(const dmnsn_canvas *canvas,
+                        unsigned int x, unsigned int y);
+void dmnsn_wrlock_pixel(dmnsn_canvas *canvas, unsigned int x, unsigned int y);
+void dmnsn_unlock_pixel(const dmnsn_canvas *canvas,
+                        unsigned int x, unsigned int y);
+
 #endif /* DIMENSION_CANVAS_H */
diff --git a/libdimension/error.c b/libdimension/error.c
new file mode 100644
index 0000000..b91c192
--- /dev/null
+++ b/libdimension/error.c
@@ -0,0 +1,74 @@
+/*************************************************************************
+ * Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of Dimension.                                       *
+ *                                                                       *
+ * Dimension is free software; you can redistribute it and/or modify it  *
+ * under the terms of the GNU Lesser General Public License as published *
+ * by the Free Software Foundation; either version 3 of the License, or  *
+ * (at your option) any later version.                                   *
+ *                                                                       *
+ * Dimension is distributed in the hope that it will be useful, but      *
+ * WITHOUT ANY WARRANTY; without even the implied warranty of            *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+#include "dimension.h"
+#include <pthread.h>
+#include <stdio.h>  /* For fprintf() */
+#include <stdlib.h> /* For exit()    */
+
+static dmnsn_severity dmnsn_resilience = DMNSN_SEVERITY_MEDIUM;
+static pthread_mutex_t dmnsn_resilience_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+void
+dmnsn_report_error(dmnsn_severity severity, const char *func, const char *str)
+{
+  if (severity >= dmnsn_get_resilience()) {
+    fprintf(stderr, "Dimension ERROR:   %s(): %s\n", func, str);
+    exit(1);
+  } else {
+    fprintf(stderr, "Dimension WARNING: %s(): %s\n", func, str);
+  }
+}
+
+dmnsn_severity
+dmnsn_get_resilience()
+{
+  dmnsn_severity resilience;
+  if (pthread_mutex_lock(&dmnsn_resilience_mutex) != 0) {
+    fprintf(stderr, "Dimension WARNING: %s(): %s\n", __func__,
+            "Couldn't lock resilience mutex.");
+  }
+  resilience = dmnsn_resilience;
+  if (pthread_mutex_unlock(&dmnsn_resilience_mutex) != 0) {
+    fprintf(stderr, "Dimension WARNING: %s(): %s\n", __func__,
+            "Couldn't unlock resilience mutex.");
+  }
+  return resilience;
+}
+
+void
+dmnsn_set_resilience(dmnsn_severity resilience)
+{
+  if (resilience > DMNSN_SEVERITY_HIGH) {
+    fprintf(stderr, "Dimension ERROR: %s(): %s\n", __func__,
+            "Resilience has wrong value.");
+    exit(1);
+  }
+
+  if (pthread_mutex_lock(&dmnsn_resilience_mutex) != 0) {
+    fprintf(stderr, "Dimension WARNING: %s(): %s\n", __func__,
+            "Couldn't lock resilience mutex.");
+  }
+  dmnsn_resilience = resilience;
+  if (pthread_mutex_unlock(&dmnsn_resilience_mutex) != 0) {
+    fprintf(stderr, "Dimension WARNING: %s(): %s\n", __func__,
+            "Couldn't unlock resilience mutex.");
+  }
+}