[Qemu-devel] [PATCH 1/3] curl: Fix parsing of readahead option from filename

[Matthew Booth]

curl_parse_filename wasn't removing the option string from the url,
resulting in a 404.

This change is a essentially a rewrite of that function as I also need
to extend it to handle more options. The rewrite is also much easier
to read.

Signed-off-by: Matthew Booth <address@hidden>
---
 block/curl.c | 81 ++++++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 52 insertions(+), 29 deletions(-)

diff --git a/block/curl.c b/block/curl.c
index d2f1084..4de6856 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -46,12 +46,15 @@
 #define CURL_NUM_STATES 8
 #define CURL_NUM_ACB    8
 #define SECTOR_SIZE     512
-#define READ_AHEAD_SIZE (256 * 1024)
+#define READ_AHEAD_DEFAULT (256 * 1024)
 
 #define FIND_RET_NONE   0
 #define FIND_RET_OK     1
 #define FIND_RET_WAIT   2
 
+#define CURL_BLOCK_OPT_URL       "url"
+#define CURL_BLOCK_OPT_READAHEAD "readahead"
+
 struct BDRVCURLState;
 
 typedef struct CURLAIOCB {
@@ -396,41 +399,60 @@ static void curl_clean_state(CURLState *s)
 static void curl_parse_filename(const char *filename, QDict *options,
                                 Error **errp)
 {
-
-    #define RA_OPTSTR ":readahead="
     char *file;
-    char *ra;
-    const char *ra_val;
-    int parse_state = 0;
+    char *end;
 
     file = g_strdup(filename);
+    end = file + strlen(file) - 1;
+
+    /* Don't fail if we've been passed an empty string.
+     * Only examine strings with a trailing ':'
+     */
+    if (end >= file && *end == ':') {
+        /* We exit this loop when we don't find a recognised option immediately
+         * preceding the trailing ':' of the form ':<option>=<value>'
+         *
+         * If filename has a trailing ':' but no preceding options, we don't
+         * remove the trailing ':'.
+         */
+        for (;;) {
+            /* Look for the preceding colon */
+            char *colon = memrchr(file, ':', end - file);
+            if (NULL == colon) {
+                break;
+            }
 
-    /* Parse a trailing ":readahead=#:" param, if present. */
-    ra = file + strlen(file) - 1;
-    while (ra >= file) {
-        if (parse_state == 0) {
-            if (*ra == ':') {
-                parse_state++;
-            } else {
+            char *opt_start = colon + 1;
+
+            /* Look for an equals sign */
+            char *equals = memchr(opt_start, '=', end - opt_start);
+            if (NULL == equals) {
                 break;
             }
-        } else if (parse_state == 1) {
-            if (*ra > '9' || *ra < '0') {
-                char *opt_start = ra - strlen(RA_OPTSTR) + 1;
-                if (opt_start > file &&
-                    strncmp(opt_start, RA_OPTSTR, strlen(RA_OPTSTR)) == 0) {
-                    ra_val = ra + 1;
-                    ra -= strlen(RA_OPTSTR) - 1;
-                    *ra = '\0';
-                    qdict_put(options, "readahead", qstring_from_str(ra_val));
-                }
+
+            size_t opt_len = equals - opt_start;
+            char *value = equals + 1;
+            size_t value_len = end - value;
+
+            if (opt_len == strlen(CURL_BLOCK_OPT_READAHEAD) &&
+                memcmp(opt_start, CURL_BLOCK_OPT_READAHEAD, opt_len) == 0) {
+                /* This is redundant after the first iteration */
+                *end = '\0';
+                qdict_put(options, CURL_BLOCK_OPT_READAHEAD,
+                          qstring_from_str(value));
+            } else {
+                /* Unknown option */
                 break;
             }
+
+            end = colon;
+
+            /* We've found at least 1 option. Remove the trailing ':' */
+            *end = '\0';
         }
-        ra--;
     }
 
-    qdict_put(options, "url", qstring_from_str(file));
+    qdict_put(options, CURL_BLOCK_OPT_URL, qstring_from_str(file));
 
     g_free(file);
 }
@@ -440,12 +462,12 @@ static QemuOptsList runtime_opts = {
     .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
     .desc = {
         {
-            .name = "url",
+            .name = CURL_BLOCK_OPT_URL,
             .type = QEMU_OPT_STRING,
             .help = "URL to open",
         },
         {
-            .name = "readahead",
+            .name = CURL_BLOCK_OPT_READAHEAD,
             .type = QEMU_OPT_SIZE,
             .help = "Readahead size",
         },
@@ -477,14 +499,15 @@ static int curl_open(BlockDriverState *bs, QDict 
*options, int flags,
         goto out_noclean;
     }
 
-    s->readahead_size = qemu_opt_get_size(opts, "readahead", READ_AHEAD_SIZE);
+    s->readahead_size = qemu_opt_get_size(opts, CURL_BLOCK_OPT_READAHEAD,
+                                          READ_AHEAD_DEFAULT);
     if ((s->readahead_size & 0x1ff) != 0) {
         error_setg(errp, "HTTP_READAHEAD_SIZE %zd is not a multiple of 512",
                    s->readahead_size);
         goto out_noclean;
     }
 
-    file = qemu_opt_get(opts, "url");
+    file = qemu_opt_get(opts, CURL_BLOCK_OPT_URL);
     if (file == NULL) {
         error_setg(errp, "curl block driver requires an 'url' option");
         goto out_noclean;
-- 
1.9.0