cubeb: Intern string support.

A simple database for interned strings.  This is to be used to provide
stable device ids in the device enumeration API.

2 files changed, 197 insertions, 0 deletions

diff --git a/src/cubeb_strings.c b/src/cubeb_strings.c
new file mode 100644
index 0000000..79d7d21
--- /dev/null
+++ b/src/cubeb_strings.c
@@ -0,0 +1,155 @@
+/*
+ * Copyright © 2011 Mozilla Foundation
+ *
+ * This program is made available under an ISC-style license.  See the
+ * accompanying file LICENSE for details.
+ */
+
+#include "cubeb_strings.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define CUBEB_STRINGS_INLINE_COUNT 4
+
+struct cubeb_strings {
+  uint32_t size;
+  uint32_t count;
+  char ** data;
+  char * small_store[CUBEB_STRINGS_INLINE_COUNT];
+};
+
+int
+cubeb_strings_init(cubeb_strings ** strings)
+{
+  cubeb_strings* strs = NULL;
+
+  if (!strings) {
+    return CUBEB_ERROR;
+  }
+
+  strs = calloc(1, sizeof(cubeb_strings));
+  assert(strs);
+
+  if (!strs) {
+    return CUBEB_ERROR;
+  }
+
+  strs->size = sizeof(strs->small_store) / sizeof(strs->small_store[0]);
+  strs->count = 0;
+  strs->data = strs->small_store;
+
+  *strings = strs;
+
+  return CUBEB_OK;
+}
+
+void
+cubeb_strings_destroy(cubeb_strings * strings)
+{
+  char ** sp = NULL;
+  char ** se = NULL;
+
+  if (!strings) {
+    return;
+  }
+
+  sp = strings->data;
+  se = sp + strings->count;
+
+  for ( ;  sp != se; sp++) {
+    if (*sp) {
+      free(*sp);
+    }
+  }
+
+  if (strings->data != strings->small_store) {
+    free(strings->data);
+  }
+
+  free(strings);
+}
+
+/** Look for string in string storage.
+    @param strings Opaque pointer to interned string storage.
+    @param s String to look up.
+    @retval Read-only string or NULL if not found. */
+static char const *
+cubeb_strings_lookup(cubeb_strings * strings, char const * s)
+{
+  char ** sp = NULL;
+  char ** se = NULL;
+
+  if (!strings || !s) {
+    return NULL;
+  }
+
+  sp = strings->data;
+  se = sp + strings->count;
+
+  for ( ; sp != se; sp++) {
+    if (*sp && strcmp(*sp, s) == 0) {
+      return *sp;
+    }
+  }
+
+  return NULL;
+}
+
+static char const *
+cubeb_strings_push(cubeb_strings * strings, char const * s)
+{
+  char * is = NULL;
+
+  if (strings->count == strings->size) {
+    char ** new_data;
+    uint32_t value_size = sizeof(char const *);
+    uint32_t new_size = strings->size * 2;
+    if (!new_size || value_size > (uint32_t)-1 / new_size) {
+      // overflow
+      return NULL;
+    }
+
+    if (strings->small_store == strings->data) {
+      // First time heap allocation.
+      new_data = malloc(new_size * value_size);
+      if (new_data) {
+        memcpy(new_data, strings->small_store, sizeof(strings->small_store));
+      }
+    } else {
+      new_data = realloc(strings->data, new_size * value_size);
+    }
+
+    if (!new_data) {
+      // out of memory
+      return NULL;
+    }
+
+    strings->size = new_size;
+    strings->data = new_data;
+  }
+
+  is = strdup(s);
+  strings->data[strings->count++] = is;
+
+  return is;
+}
+
+char const *
+cubeb_strings_intern(cubeb_strings * strings, char const * s)
+{
+  char const * is = NULL;
+
+  if (!strings || !s) {
+    return NULL;
+  }
+
+  is = cubeb_strings_lookup(strings, s);
+  if (is) {
+    return is;
+  }
+
+  return cubeb_strings_push(strings, s);
+}
+
diff --git a/src/cubeb_strings.h b/src/cubeb_strings.h
new file mode 100644
index 0000000..f8ad2fe
--- /dev/null
+++ b/src/cubeb_strings.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright © 2011 Mozilla Foundation
+ *
+ * This program is made available under an ISC-style license.  See the
+ * accompanying file LICENSE for details.
+ */
+
+#ifndef CUBEB_STRINGS_H
+#define CUBEB_STRINGS_H
+
+#include "cubeb/cubeb.h"
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+/** Opaque handle referencing interned string storage. */
+typedef struct cubeb_strings cubeb_strings;
+
+/** Initialize a interned string structure.
+    @param strings An out param where an opaque pointer to the
+    interned string storage will be returned.
+    @retval CUBEB_OK in case of success.
+    @retval CUBEB_ERROR in case of error. */
+CUBEB_EXPORT int cubeb_strings_init(cubeb_strings ** strings);
+
+/** */
+CUBEB_EXPORT void cubeb_strings_destroy(cubeb_strings * strings);
+
+/** Add string to internal storage.
+    @param strings Opaque pointer to interned string storage.
+    @param s String to add to storage.
+    @retval CUBEB_OK
+    @retval CUBEB_ERROR
+ */
+CUBEB_EXPORT char const * cubeb_strings_intern(cubeb_strings * strings, char const * s);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif // !CUBEB_STRINGS_H