realloc-buffer: add three new helpers

realloc_buffer_append_byte() does what the name suggests: appends one
byte to the realloc buffer.

realloc_buffer_read_full() reads data off an fd until EOF is reached.

realloc_buffer_memchr() searchs the buffer for a character.

Author: poettering

src/realloc-buffer.c

@@ -243,6 +243,23 @@ int realloc_buffer_read_size(ReallocBuffer *b, int fd, size_t add) {
         return l > 0;
 }
 
+int realloc_buffer_read_full(ReallocBuffer *b, int fd, size_t limit) {
+        int r;
+
+        /* Reads from "fd" until EOF is hit, but never more than "limit" */
+
+        for (;;) {
+                if (limit != (size_t) -1 && realloc_buffer_size(b) > limit)
+                        return -E2BIG;
+
+                r = realloc_buffer_read(b, fd);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return 0;
+        }
+}
+
 int realloc_buffer_read_target(ReallocBuffer *b, int fd, size_t target_size) {
         int r;
 
@@ -392,3 +409,31 @@ int realloc_buffer_printf(ReallocBuffer *b, const char *fmt, ...) {
         }
 
 }
+
+int realloc_buffer_memchr(ReallocBuffer *buffer, uint8_t c) {
+        const uint8_t *p, *q;
+        size_t l, d;
+        int ret;
+
+        /* Looks for byte 'c' in the buffer. Returns -ENXIO when we can't find the byte. Returns an index >= 0 if
+         * found. Returns -EOVERFLOW if found but the index doesn't fit in "int" */
+
+        l = realloc_buffer_size(buffer);
+        if (l <= 0)
+                return -ENXIO;
+
+        p = realloc_buffer_data(buffer);
+        q = memchr(p, c, l);
+        if (!q)
+                return -ENXIO;
+
+        d = (size_t) (q - p);
+        ret = (int) d;
+
+        if (_unlikely_(ret < 0))
+                return -EOVERFLOW;
+        if (_unlikely_((size_t) ret != d))
+                return -EOVERFLOW;
+
+        return ret;
+}

src/realloc-buffer.h

@@ -56,6 +56,10 @@ void* realloc_buffer_extend(ReallocBuffer *b, size_t size);
 void* realloc_buffer_extend0(ReallocBuffer *b, size_t size);
 void* realloc_buffer_append(ReallocBuffer *b, const void *p, size_t size);
 
+static inline void* realloc_buffer_append_byte(ReallocBuffer *b, uint8_t q) {
+        return realloc_buffer_append(b, &q, sizeof(q));
+}
+
 void realloc_buffer_free(ReallocBuffer *b);
 
 static inline void realloc_buffer_empty(ReallocBuffer *b) {
@@ -72,6 +76,8 @@ static inline int realloc_buffer_read(ReallocBuffer *b, int fd) {
         return realloc_buffer_read_size(b, fd, (size_t) -1);
 }
 
+int realloc_buffer_read_full(ReallocBuffer *b, int fd, size_t limit);
+
 int realloc_buffer_write(ReallocBuffer *b, int fd);
 int realloc_buffer_write_maybe(ReallocBuffer *b, int fd);
 
@@ -83,4 +89,6 @@ void* realloc_buffer_donate(ReallocBuffer *b, void *p, size_t size);
 
 int realloc_buffer_printf(ReallocBuffer *b, const char *fmt, ...) _printf_(2,3);
 
+int realloc_buffer_memchr(ReallocBuffer *buffer, uint8_t c);
+
 #endif