Improve string parsing code

Currently next_string and next_hexstring functions use a static
buffer in the iterator to store the value.  This value is clobbered
as soon as next_string or next_hexstring is called.  Instead,
we copy the entire line in iter_next and use it as a scratch buffer.
The only limitation is that lines of max 2048 are possible, however
these are limited to around this size by parts of the standard.

diff --git a/gatchat/gatresult.c b/gatchat/gatresult.c
index 8da8821..7a98308 100644 (file)
--- a/gatchat/gatresult.c
+++ b/gatchat/gatresult.c
@@ -43,13 +43,18 @@ gboolean g_at_result_iter_next(GAtResultIter *iter, const char *prefix)
 {
        char *line;
        int prefix_len = prefix ? strlen(prefix) : 0;
+       int linelen;
 
        while ((iter->l = iter->l->next)) {
                line = iter->l->data;
+               linelen = strlen(line);
+
+               if (linelen > G_AT_RESULT_LINE_LENGTH_MAX)
+                       continue;
 
                if (prefix_len == 0) {
                        iter->line_pos = 0;
-                       return TRUE;
+                       goto out;
                }
 
                if (g_str_has_prefix(line, prefix) == FALSE)
@@ -61,10 +66,15 @@ gboolean g_at_result_iter_next(GAtResultIter *iter, const char *prefix)
                        line[iter->line_pos] == ' ')
                        iter->line_pos += 1;
 
-               return TRUE;
+               goto out;
        }
 
        return FALSE;
+
+out:
+       /* Already checked the length to be no more than buflen */
+       strcpy(iter->buf, line);
+       return TRUE;
 }
 
 const char *g_at_result_iter_raw_line(GAtResultIter *iter)
@@ -116,7 +126,7 @@ gboolean g_at_result_iter_next_string(GAtResultIter *iter, const char **str)
        /* Omitted string */
        if (line[pos] == ',') {
                end = pos;
-               memset(iter->buf, 0, sizeof(iter->buf));
+               iter->buf[pos] = '\0';
                goto out;
        }
 
@@ -131,11 +141,7 @@ gboolean g_at_result_iter_next_string(GAtResultIter *iter, const char **str)
        if (line[end] != '"')
                return FALSE;
 
-       if (end - pos >= sizeof(iter->buf))
-               return FALSE;
-
-       strncpy(iter->buf, line+pos, end-pos);
-       memset(iter->buf + end - pos, 0, sizeof(iter->buf) - end + pos);
+       iter->buf[end] = '\0';
 
        /* Skip " */
        end += 1;
@@ -144,7 +150,7 @@ out:
        iter->line_pos = skip_to_next_field(line, end, len);
 
        if (str)
-               *str = iter->buf;
+               *str = iter->buf + pos;
 
        return TRUE;
 }
@@ -172,7 +178,7 @@ gboolean g_at_result_iter_next_hexstring(GAtResultIter *iter,
        /* Omitted string */
        if (line[pos] == ',') {
                end = pos;
-               memset(iter->buf, 0, sizeof(iter->buf));
+               iter->buf[pos] = '\0';
                goto out;
        }
 
@@ -184,19 +190,16 @@ gboolean g_at_result_iter_next_hexstring(GAtResultIter *iter,
        if ((end - pos) & 1)
                return FALSE;
 
-       if ((end - pos) / 2 >= sizeof(iter->buf))
-               return FALSE;
        *length = (end - pos) / 2;
 
-       for (bufpos = iter->buf; pos < end; pos += 2)
+       for (bufpos = iter->buf + pos; pos < end; pos += 2)
                sscanf(line + pos, "%02hhx", bufpos++);
-       memset(bufpos, 0, sizeof(iter->buf) - (bufpos - iter->buf));
 
 out:
        iter->line_pos = skip_to_next_field(line, end, len);
 
        if (str)
-               *str = (guint8 *) iter->buf;
+               *str = (guint8 *) bufpos - *length;
 
        return TRUE;
 }

diff --git a/gatchat/gatresult.h b/gatchat/gatresult.h
index cbe6d05..fc4c123 100644 (file)
--- a/gatchat/gatresult.h
+++ b/gatchat/gatresult.h
@@ -33,10 +33,12 @@ struct _GAtResult {
 
 typedef struct _GAtResult GAtResult;
 
+#define G_AT_RESULT_LINE_LENGTH_MAX 2048
+
 struct _GAtResultIter {
        GAtResult *result;
        GSList *l;
-       char buf[2048];
+       char buf[G_AT_RESULT_LINE_LENGTH_MAX + 1];
        unsigned int line_pos;
        GSList pre;
 };