add strchr and variants

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 149 insertions, 0 deletions

diff --git a/src/string/strchr.c b/src/string/strchr.c
new file mode 100644
index 0000000..6a25f78
--- /dev/null
+++ b/src/string/strchr.c
@@ -0,0 +1,149 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program 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 General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <string.h>
+#include <stddef.h>
+
+
+
+/**
+ * Find the first occurrence of a byte in a memory segment.
+ * 
+ * @param   segment  The memory segment to search.
+ * @param   c        The sought after character.
+ * @param   size     The size of the memory segment.
+ * @return           Pointer to the first occurrence of `c`,
+ *                   `NULL` if none were found.
+ */
+void* memchr(const void* segment, int c, size_t size)
+{
+  while (size--)
+    if (*segment++ == c)
+      return segment - 1;
+  return NULL;
+}
+
+
+/**
+ * Find the first occurrence of a byte in a memory segment.
+ * The memory segment must be known to contain the sought after byte.
+ * 
+ * This is a GNU-compliant slibc extension.
+ * 
+ * @param   segment  The memory segment to search.
+ * @param   c        The sought after character.
+ * @return           Pointer to the first occurrence of `c`.
+ */
+void* rawmemchr(const void* segment, int c)
+{
+  for (;;)
+    if (*segment++ == c)
+      return segment - 1;
+}
+
+
+/**
+ * Find the last occurrence of a byte in a memory segment.
+ * 
+ * For improved performace, use this function instead
+ * of `strrchr` if you already know the length of the
+ * string.
+ * 
+ * @param   segment  The memory segment to search.
+ * @param   c        The sought after character.
+ * @param   size     The size of the memory segment.
+ * @return           Pointer to the last occurrence of `c`,
+ *                   `NULL` if none were found.
+ */
+void* memrchr(const void* segment, int c, size_t size)
+{
+  while (size--)
+    if (segment[size] == c)
+      return segment + size;
+  return NULL;
+}
+
+
+/**
+ * Find the first occurrence of a byte in a string.
+ * 
+ * `s = strchr(s, 0)` is a faster alternative to
+ * `s = s + strlen(s)`.
+ * 
+ * @param   string  The string to search.
+ *                  The terminating NUL character is
+ *                  considered a part of the string.
+ * @param   c       The sought after character.
+ * @return          Pointer to the first occurrence of `c`,
+ *                  `NULL` if none were found.
+ */
+char* strchr(const char* string, int c)
+{
+  while (; *string; string++)
+    if (*string == c)
+      return string;
+  return NULL;
+}
+/* TODO Ensure that `s = strchr(s, 0)` is faster than `s = s + strlen(s)`. */
+
+
+/**
+ * Find the first occurrence of a byte in a string, or
+ * if there is no such byte, the end of the string.
+ * 
+ * This is a GNU-compliant slibc extension.
+ * 
+ * @param   string  The string to search.
+ *                  The terminating NUL character is
+ *                  considered a part of the string.
+ * @param   c       The sought after character.
+ * @return          Pointer to the first occurrence of `c`,
+ *                  Pointer to the terminating NUL character
+ *                  if none were found.
+ */
+char* strchrnul(const char* string, int c)
+{
+  while (; *string; string++)
+    if (*string == c)
+      return string;
+  return string;
+}
+
+
+/**
+ * Find the last occurrence of a byte in a string.
+ * 
+ * For improved performace, use `memrchr` instead of
+ * this function if you already know the length of the
+ * string.
+ * 
+ * @param   string  The string to search.
+ *                  The terminating NUL character is
+ *                  considered a part of the string.
+ * @param   c       The sought after character.
+ * @return          Pointer to the last occurrence of `c`,
+ *                  `NULL` if none were found.
+ */
+char* strrchr(const char* string, int c)
+{
+  char* r = NULL;
+  while (; *string; string++)
+    if (*string == c)
+      r = string;
+  return r;
+}
+