strbuf: added strbuf_avail and strbuf_appendf.

Makefile.include

@@ -20,7 +20,7 @@ ifdef NO_MEMRCHR
 endif
 obj-xalloc = src/xalloc.o src/die.o
 obj-str-list = src/str-list.o $(obj-xalloc)
-obj-strbuf = src/strbuf.o $(obj-xalloc)
+obj-strbuf = src/strbuf.o $(obj-xalloc) src/die.o
 obj-path = src/path.o $(obj-strbuf)
 obj-rbtree = src/rbtree.o $(obj-xalloc)
 obj-fscrawl = src/fscrawl.o $(obj-strbuf) $(obj-path) $(obj-log)

docs/technical/strbuf.txt

@@ -30,11 +30,19 @@ Functions
     This function will not allocate memory, it only sets ->len and
     assure that the string is null-terminated at the new position.
 
+`strbuf_avail()`::
+
+    Returns the number of characters that are allocated but not used in the buffer.
+
 `strbuf_append()`::
 
     This function will append the buffer with the contents of 'ptr'
     and will always copy exactly 'len' bytes. (if memory can be obtained ofcourse)
 
+`strbuf_appendf()`::
+
+    Adds the formated-string 'fmt' to the end of ->buf.
+
 `strbuf_append_str()`::
 
     Will add the 'str' C-string to the end of ->buf

src/strbuf.c

@@ -9,7 +9,10 @@
  */
 
 #include <ctype.h>
+#include <stdio.h>
+#include <stdarg.h>
 #include "compat/string.h"
+#include "util.h"
 #include "xalloc.h"
 #include "strbuf.h"
 
@@ -23,6 +26,11 @@ void strbuf_init(strbuf_t *s) {
 	s->alloc_size = s->len = 0;
 }
 
+size_t strbuf_avail(strbuf_t *s) {
+    
+    return s->alloc_size ? s->alloc_size - (s->len + 1) : 0;
+}
+
 void strbuf_expand(strbuf_t *s, size_t len) {
 
     if (s->len + len + 1 < s->alloc_size)
@@ -112,6 +120,32 @@ void strbuf_append(strbuf_t *s, const void *ptr, size_t len) {
     s->buf[s->len] = '\0';
 }
 
+void strbuf_appendf(strbuf_t *s, const char *fmt, ...) {
+
+    va_list vl;
+    int len;
+
+    if (!strbuf_avail(s))
+        strbuf_expand(s, CHNK_SIZE-1);
+
+    va_start(vl, fmt);
+    len = vsnprintf(s->buf + s->len, s->alloc_size - s->len, fmt, vl);
+    va_end(vl);
+
+    if (len < 0)
+        die_errno("vsnprintf");
+    if (len > strbuf_avail(s)) {
+        strbuf_expand(s, len);
+        va_start(vl, fmt);
+        len = vsnprintf(s->buf + s->len, s->alloc_size - s->len, fmt, vl);
+        va_end(vl);
+        if (len > strbuf_avail(s))
+            die_errno("vsnprintf");
+    }
+    s->len += len;
+    s->buf[len] = '\0';
+}
+
 void strbuf_append_str(strbuf_t *s, const char *str) {
 
     strbuf_append(s, str, strlen(str));

src/strbuf.h

@@ -25,6 +25,8 @@ extern char strbuf_null;
 
 void strbuf_init(strbuf_t *s);
 
+size_t strbuf_avail(strbuf_t *s);
+
 void strbuf_expand(strbuf_t *s, size_t len);
 
 void strbuf_reduce(strbuf_t *s, size_t len);
@@ -41,6 +43,8 @@ void strbuf_attach(strbuf_t *s, void *str, size_t len, size_t alloc_size);
 
 void strbuf_append(strbuf_t *s, const void *ptr, size_t len);
 
+void strbuf_appendf(strbuf_t *s, const char *fmt, ...);
+
 void strbuf_append_str(strbuf_t *s, const char *str);
 
 void strbuf_append_ch(strbuf_t *s, char ch);

test/t_strbuf.c

@@ -39,6 +39,17 @@ void test_setlen() {
     strbuf_free(&b);
 }
 
+void test_appendf() {
+
+    strbuf_t b = STRBUF_INIT;
+
+    strbuf_appendf(&b, "%s %i", "string", 32);
+
+    print_strbuf(&b);
+
+    strbuf_free(&b);
+}
+
 void test_release() {
 
     strbuf_t b = STRBUF_INIT;
@@ -216,6 +227,7 @@ void test_free_empty() {
 
 int main() {
 
+    test_appendf();
     test_release_empty();
     test_release();
     test_setlen();