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json buffering and parsing

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Signed-off-by: Toni Uhlig <matzeton@googlemail.com>
This commit is contained in:
Toni Uhlig
2020-08-04 22:38:08 +02:00
parent 8a6021268e
commit d828ef1bf0
2 changed files with 104 additions and 9 deletions
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104
examples/c-json-stdout/c-json-stdout.c
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@@ -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;