Add h3prio example: parse HTTP/3 Priority Parameters

Author: Dmitri Tikhonov

Makefile

@@ -1,12 +1,15 @@
 CFLAGS=-Wall
 
-all: test-sfp
+all: test-sfp h3prio
 
 fuzz: fuzz-sfp
 
 test-sfp: test-sfp.c ls-sfparser.c ls-sfparser.h
 	cc ${CFLAGS} -o test-sfp test-sfp.c ls-sfparser.c
 
+h3prio: h3prio.c ls-sfparser.c ls-sfparser.h
+	cc ${CFLAGS} -o h3prio h3prio.c ls-sfparser.c
+
 fuzz-sfp: fuzz-sfp.c ls-sfparser.c ls-sfparser.h
 	afl-gcc -O3 -o fuzz-sfp fuzz-sfp.c ls-sfparser.c
 	#cc -g3 -o fuzz-sfp fuzz-sfp.c ls-sfparser.c
@@ -17,4 +20,4 @@ ls-sfparser.c: ls-sfparser.l
 	flex -o ls-sfparser.c ls-sfparser.l
 
 clean:
-	rm -vf test-sfp fuzz-sfp
+	rm -vf test-sfp fuzz-sfp h3prio

h3prio.c

@@ -0,0 +1,110 @@
+/* Parse HTTP/3 Priority Parameters
+ *
+ * See
+ *  https://tools.ietf.org/html/draft-ietf-httpbis-priority-01
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "ls-sfparser.h"
+
+
+struct prio {
+    enum {
+        URG_SET  = 1 << 0,  /* True if `urgency' is set */
+        INC_SET  = 1 << 1,  /* True if `incremental' is set */
+        URG_NAME = 1 << 2,  /* True if previous element dictionary name "u" */
+        INC_NAME = 1 << 3,  /* True if previous element dictionary name "i" */
+    }           flags;
+    unsigned    urgency;
+    bool        incremental;
+};
+
+
+static int
+callback (void *user_data, enum ls_sf_dt type, char *str, size_t len, int off)
+{
+    struct prio *const prio = user_data;
+
+    if (type == LS_SF_DT_NAME)
+    {
+        if (1 == len)
+            switch (str[0])
+            {
+                case 'u': prio->flags |= URG_NAME; return 0;
+                case 'i': prio->flags |= INC_NAME; return 0;
+            }
+    }
+    else if (prio->flags & URG_NAME)
+    {
+        if (type == LS_SF_DT_INTEGER)
+        {
+            prio->urgency = atoi(str);
+            if (prio->urgency <= 7)
+                prio->flags |= URG_SET;
+            else
+            {
+                printf("invalid value of urgency: %.*s\n", (int) len, str);
+                return -1;
+            }
+        }
+        else
+        {
+            printf("invalid type of urgency: %s\n", ls_sf_dt2str[type]);
+            return -1;
+        }
+    }
+    else if (prio->flags & INC_NAME)
+    {
+        if (type == LS_SF_DT_BOOLEAN)
+        {
+            prio->flags |= INC_SET;
+            prio->incremental = str[0] - '0';
+        }
+        else
+        {
+            printf("invalid type of incremental: %s\n", ls_sf_dt2str[type]);
+            return -1;
+        }
+    }
+    prio->flags &= ~(INC_NAME|URG_NAME);
+
+    return 0;
+}
+
+
+int
+main (int argc, char **argv)
+{
+    struct prio prio;
+    int ret;
+
+    if (argc != 2)
+    {
+        printf("Usage: %s 'HTTP/3 priority parameters'\n", argv[0]);
+        return 1;
+    }
+
+    memset(&prio, 0, sizeof(prio));
+    ret = ls_sf_parse(LS_SF_TLT_DICTIONARY, argv[1], strlen(argv[1]), callback,
+                                                &prio, NULL, 0);
+    if (ret == 0)
+    {
+        printf("parsing successful\n");
+        if (prio.flags & URG_SET)
+            printf("urgency: %u\n", prio.urgency);
+        else
+            printf("urgency: <not set>\n");
+        if (prio.flags & INC_SET)
+            printf("incremental: %i\n", (int) prio.incremental);
+        else
+            printf("incremental: <not set>\n");
+    }
+    else
+        printf("parsing failed\n");
+
+    return ret ? -1 : 0;
+}