json buffering and parsing

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

1 files changed, 95 insertions, 9 deletions

diff --git a/examples/c-json-stdout/c-json-stdout.c b/examples/c-json-stdout/c-json-stdout.c
index ff84a6411..d3a312030 100644
--- a/examples/c-json-stdout/c-json-stdout.c
+++ b/examples/c-json-stdout/c-json-stdout.c
@@ -1,12 +1,16 @@
 #include <arpa/inet.h>
 #include <errno.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "config.h"
+#ifdef USE_JSON
 #include "jsmn/jsmn.h"
+#endif
 
 static char serv_listen_addr[INET_ADDRSTRLEN] = DISTRIBUTOR_HOST;
 static uint16_t serv_listen_port = DISTRIBUTOR_PORT;
@@ -17,35 +21,117 @@ int main(void)
     struct sockaddr_in remote_addr = {};
     socklen_t remote_addrlen = sizeof(remote_addr);
     uint8_t buf[NETWORK_BUFFER_MAX_SIZE];
-    //size_t buf_used = 0;
-    //unsigned long long int buf_wanted = 0;
+    size_t buf_used = 0;
+    size_t json_start = 0;
+    unsigned long long int buf_wanted = 0;
+#ifdef USE_JSON
+    jsmn_parser parser;
+    jsmntok_t tokens[128];
+#endif
 
-    if (sockfd < 0) {
+    if (sockfd < 0)
+    {
         perror("socket");
         return 1;
     }
 
     remote_addr.sin_family = AF_INET;
-    if (inet_pton(AF_INET, &serv_listen_addr[0], &remote_addr.sin_addr) != 1) {
+    if (inet_pton(AF_INET, &serv_listen_addr[0], &remote_addr.sin_addr) != 1)
+    {
         perror("inet_pton");
         return 1;
     }
     remote_addr.sin_port = htons(serv_listen_port);
 
-    if (connect(sockfd, (struct sockaddr *) &remote_addr, remote_addrlen) != 0) {
+    if (connect(sockfd, (struct sockaddr *)&remote_addr, remote_addrlen) != 0)
+    {
         perror("connect");
         return 1;
     }
 
-    while (1) {
+    while (1)
+    {
         errno = 0;
-        ssize_t bytes_read = read(sockfd, buf, sizeof(buf));
+        ssize_t bytes_read = read(sockfd, buf + buf_used, sizeof(buf) - buf_used);
 
-        if (bytes_read <= 0 || errno != 0) {
+        if (bytes_read <= 0 || errno != 0)
+        {
             break;
         }
 
-        printf("RECV[%zd]: '%.*s'\n\n", bytes_read, (int) bytes_read, buf);
+        buf_used += bytes_read;
+        if (buf_wanted == 0)
+        {
+            char * json_str_start = NULL;
+            errno = 0;
+            /* the first bytes are the textual representation of the following JSON string */
+            buf_wanted = strtoull((char *)buf, &json_str_start, 10);
+            json_start = (uint8_t *)json_str_start - buf;
+            buf_wanted += json_start;
+
+            if (errno == ERANGE)
+            {
+                buf_used = 0;
+                buf_wanted = 0;
+                fprintf(stderr, "Size of JSON exceeds limit\n");
+                continue;
+            }
+            if ((uint8_t *)json_str_start == buf)
+            {
+                fprintf(stderr, "Missing size before JSON string: %.*s\n", (int)buf_used, buf);
+                buf_used = 0;
+                buf_wanted = 0;
+                continue;
+            }
+            if (buf_wanted > sizeof(buf))
+            {
+                fprintf(stderr, "BUG: JSON string too big: %llu > %zu\n", buf_wanted, sizeof(buf));
+                buf_used = 0;
+                buf_wanted = 0;
+                continue;
+            }
+        }
+
+        /* buffered enough data (full JSON String) ? */
+        if (buf_wanted > buf_used)
+        {
+            continue;
+        }
+        /* after buffering complete, last character should always be a '}' (end of object) */
+        if (buf[buf_wanted - 1] != '}')
+        {
+            fprintf(stderr, "Invalid JSON string: %.*s\n", (int)buf_wanted, buf);
+            buf_used = 0;
+            buf_wanted = 0;
+            continue;
+        }
+
+#ifdef USE_JSON
+        int r;
+        jsmn_init(&parser);
+        r = jsmn_parse(&parser, (char *)(buf + json_start), buf_wanted - json_start,
+                       tokens, sizeof(tokens) / sizeof(tokens[0]));
+        if (r < 0 || tokens[0].type != JSMN_OBJECT) {
+            fprintf(stderr, "JSON parsing failed with return value %d at position %u\n", r, parser.pos);
+            fprintf(stderr, "JSON string: '%.*s'\n", (int)(buf_wanted - json_start), (char *)(buf + json_start));
+        }
+
+        for (int i = 1; i < r; i++) {
+            if (i % 2 ==  1) {
+                printf("[%.*s : ", tokens[i].end - tokens[i].start,
+                       (char *)(buf + json_start) + tokens[i].start);
+            } else {
+                printf("%.*s] ", tokens[i].end - tokens[i].start,
+                       (char *)(buf + json_start) + tokens[i].start);
+            }
+        }
+        printf("EoF\n");
+#else
+        printf("RECV[%llu,%zd]: '%.*s'\n\n", buf_wanted, bytes_read, (int)buf_wanted, buf);
+#endif
+        memmove(buf, buf + buf_wanted, buf_used - buf_wanted);
+        buf_used -= buf_wanted;
+        buf_wanted = 0;
     }
 
     return 0;