doc: Add tutorial

doc/github_commits.c

@@ -0,0 +1,164 @@
+#include <stdlib.h>
+#include <string.h>
+
+#include <jansson.h>
+#include <curl/curl.h>
+
+#define BUFFER_SIZE  (256 * 1024)  /* 256 KB */
+
+#define URL_FORMAT   "http://github.com/api/v2/json/commits/list/%s/%s/master"
+#define URL_SIZE     256
+
+/* Return the offset of the first newline in text or the length of
+   text if there's no newline */
+static int newline_offset(const char *text)
+{
+    const char *newline = strchr(text, '\n');
+    if(!newline)
+        return strlen(text);
+    else
+        return (int)(newline - text);
+}
+
+struct write_result
+{
+    char *data;
+    int pos;
+};
+
+static size_t write_response(void *ptr, size_t size, size_t nmemb, void *stream)
+{
+    struct write_result *result = (struct write_result *)stream;
+
+    if(result->pos + size * nmemb >= BUFFER_SIZE - 1)
+    {
+        fprintf(stderr, "error: too small buffer\n");
+        return 0;
+    }
+
+    memcpy(result->data + result->pos, ptr, size * nmemb);
+    result->pos += size * nmemb;
+
+    return size * nmemb;
+}
+
+static char *request(const char *url)
+{
+    CURL *curl;
+    CURLcode status;
+    char *data;
+    long code;
+
+    curl = curl_easy_init();
+    data = malloc(BUFFER_SIZE);
+    if(!curl || !data)
+        return NULL;
+
+    struct write_result write_result = {
+        .data = data,
+        .pos = 0
+    };
+
+    curl_easy_setopt(curl, CURLOPT_URL, url);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_response);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &write_result);
+
+    status = curl_easy_perform(curl);
+    if(status != 0)
+    {
+        fprintf(stderr, "error: unable to request data from %s:\n", url);
+        fprintf(stderr, "%s\n", curl_easy_strerror(status));
+        return NULL;
+    }
+
+    curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &code);
+    if(code != 200)
+    {
+        fprintf(stderr, "error: server responded with code %ld\n", code);
+        return NULL;
+    }
+
+    curl_easy_cleanup(curl);
+    curl_global_cleanup();
+
+    /* zero-terminate the result */
+    data[write_result.pos] = '\0';
+
+    return data;
+}
+
+int main(int argc, char *argv[])
+{
+    unsigned int i;
+    char *text;
+    char url[URL_SIZE];
+
+    json_t *root;
+    json_error_t error;
+    json_t *commits;
+
+    if(argc != 3)
+    {
+        fprintf(stderr, "usage: %s USER REPOSITORY\n\n", argv[0]);
+        fprintf(stderr, "List commits at USER's REPOSITORY.\n\n");
+        return 2;
+    }
+
+    snprintf(url, URL_SIZE, URL_FORMAT, argv[1], argv[2]);
+
+    text = request(url);
+    if(!text)
+        return 1;
+
+    root = json_loads(text, &error);
+    free(text);
+
+    if(!root)
+    {
+        fprintf(stderr, "error: on line %d: %s\n", error.line, error.text);
+        return 1;
+    }
+
+    commits = json_object_get(root, "commits");
+    if(!commits || !json_is_array(commits))
+    {
+        fprintf(stderr, "error: commits is not an array\n");
+        return 1;
+    }
+
+    for(i = 0; i < json_array_size(commits); i++)
+    {
+        json_t *commit, *id, *message;
+        const char *message_text;
+
+        commit = json_array_get(commits, i);
+        if(!json_is_object(commit))
+        {
+            fprintf(stderr, "error: commit %d is not an object\n", i + 1);
+            return 1;
+        }
+
+        id = json_object_get(commit, "id");
+        if(!id || !json_is_string(id))
+        {
+            fprintf(stderr, "error: commit %d: id is not a string\n", i + 1);
+            return 1;
+        }
+
+        message = json_object_get(commit, "message");
+        if(!message || !json_is_string(message))
+        {
+            fprintf(stderr, "error: commit %d: message is not a string\n", i + 1);
+            return 1;
+        }
+
+        message_text = json_string_value(message);
+        printf("%.8s %.*s\n",
+               json_string_value(id),
+               newline_offset(message_text),
+               message_text);
+    }
+
+    json_decref(root);
+    return 0;
+}