add strbuf_expand_dict_cb(), a helper for simple cases

The new callback function strbuf_expand_dict_cb() can be used together
with strbuf_expand() if there is only a small number of placeholders
for static replacement texts.  It expects its dictionary as an array of
placeholder+value pairs as context parameter, terminated by an entry
with the placeholder member set to NULL.

The new helper is intended to aid converting the remaining calls of
interpolate().  strbuf_expand() is smaller, more flexible and can be
used to go faster than interpolate(), so it should replace the latter.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt
index a9668e5f2d2b1a7ffac45e4111ca6d8a4818af2b..a8ee2fe6a1504b943ff9c3c51807bf0f839182b1 100644 (file)
--- a/Documentation/technical/api-strbuf.txt
+++ b/Documentation/technical/api-strbuf.txt
@@ -205,6 +205,13 @@ In order to facilitate caching and to make it possible to give
 parameters to the callback, `strbuf_expand()` passes a context pointer,
 which can be used by the programmer of the callback as she sees fit.
 
+`strbuf_expand_dict_cb`::
+
+       Used as callback for `strbuf_expand()`, expects an array of
+       struct strbuf_expand_dict_entry as context, i.e. pairs of
+       placeholder and replacement string.  The array needs to be
+       terminated by an entry with placeholder set to NULL.
+
 `strbuf_addf`::
 
        Add a formatted string to the buffer.

diff --git a/strbuf.c b/strbuf.c
index 720737d856b694bc5239f0c18af372959c99e744..13be67e4d3e38472adbff019a34e3f5ce9621dd7 100644 (file)
--- a/strbuf.c
+++ b/strbuf.c
@@ -237,6 +237,22 @@ void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
        }
 }
 
+size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
+               void *context)
+{
+       struct strbuf_expand_dict_entry *e = context;
+       size_t len;
+
+       for (; e->placeholder && (len = strlen(e->placeholder)); e++) {
+               if (!strncmp(placeholder, e->placeholder, len)) {
+                       if (e->value)
+                               strbuf_addstr(sb, e->value);
+                       return len;
+               }
+       }
+       return 0;
+}
+
 size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
 {
        size_t res;

diff --git a/strbuf.h b/strbuf.h
index eba7ba423a2d3a383ef93f663c95695438269edf..b1670d99456e96b5de01918e157e10df519cae13 100644 (file)
--- a/strbuf.h
+++ b/strbuf.h
@@ -111,6 +111,11 @@ extern void strbuf_adddup(struct strbuf *sb, size_t pos, size_t len);
 
 typedef size_t (*expand_fn_t) (struct strbuf *sb, const char *placeholder, void *context);
 extern void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn, void *context);
+struct strbuf_expand_dict_entry {
+       const char *placeholder;
+       const char *value;
+};
+extern size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder, void *context);
 
 __attribute__((format(printf,2,3)))
 extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);