initial commit

Makefile

@@ -0,0 +1,2 @@
+all: main.c
+	gcc main.c -lcurl -lcjson -o isbn -Wall

main.c

@@ -0,0 +1,179 @@
+#include <curl/curl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <cjson/cJSON.h>
+
+#define BASE_URL_SIZE 38
+
+/**
+ * struct string_t
+ * char* buf - The buffer containing the string data
+ * size_t len - The length of the buffer
+ */
+typedef struct string_t {
+	char* buf;
+	size_t len;	
+} string;
+
+/**
+ * void init_string
+ * string* s - The string struct
+ *
+ * Initializes the string struct */
+void init_string (string* s)
+{
+	s->len = 0;
+	s->buf = malloc(s->len + 1);
+
+	if (NULL == s->buf) {
+		fprintf(stderr, "malloc() failed\n");
+		exit(EXIT_FAILURE);
+	}
+	s->buf[0] = '\0';
+}
+
+/**
+ * size_t writefunc
+ *
+ * The arguments come from CURLOPT_WRITEFUNCTION
+ *
+ * Writes the cURL get into the string struct
+ */
+size_t writefunc(void* ptr, size_t size, size_t nmemb, string* s)
+{
+	size_t new_len = s->len + (size * nmemb);
+	s->buf = realloc(s->buf, new_len + 1);
+	if (NULL == s->buf) {
+		fprintf(stderr, "realloc() failed\n");
+		exit(EXIT_FAILURE);
+	}	
+
+	memcpy(s->buf + s->len, ptr, size * nmemb);
+	s->buf[new_len] = '\0';
+	s->len = new_len;
+
+	return size * nmemb;
+}
+
+/**
+ * CURLcode perform_book_get
+ * char isbn_buf[14] - The ISBN
+ * string* s - The string struct to place the GET output in
+ *
+ * Perforrms a GET request with the ISBN
+ */
+CURLcode perform_book_get(char isbn_buf[14], string* s)
+{
+	CURL* handler;
+	char *base_url;
+	size_t finalurl_size = BASE_URL_SIZE + 15;
+	char finalurl[finalurl_size];
+	CURLcode result;
+
+	handler = curl_easy_init();
+	if (!handler) {
+		fprintf(stderr, "cURL failed to initialize!\n");
+		exit(EXIT_FAILURE);
+	}
+
+	base_url = "https://openlibrary.org/search.json?q=";
+	/**
+	 * Setup the URL for the request
+	 */
+	snprintf(finalurl, finalurl_size, "%s%s", base_url, isbn_buf);
+
+	curl_easy_setopt(handler, CURLOPT_URL, finalurl);
+	curl_easy_setopt(handler, CURLOPT_HTTPGET, 1L);
+	curl_easy_setopt(handler, CURLOPT_WRITEFUNCTION, writefunc);
+	curl_easy_setopt(handler, CURLOPT_WRITEDATA, s);
+
+	result = curl_easy_perform(handler);
+
+	// Always clean up	
+	curl_easy_cleanup(handler);
+
+	return result;
+}
+
+void parse_json(string* s)
+{
+	cJSON* json = cJSON_Parse(s->buf);
+	if (NULL == json) {
+		const char* error_ptr = cJSON_GetErrorPtr();
+		if (NULL != error_ptr)
+			fprintf(stderr, "JSON error: %s\n", error_ptr);
+		cJSON_Delete(json);
+		exit(EXIT_FAILURE);	
+	}
+
+	cJSON* docs = cJSON_GetObjectItemCaseSensitive(json, "docs");
+	cJSON* child = docs->child; // this is the JSON object that stores all of the books information
+
+	printf("Title: %s\n", cJSON_GetObjectItemCaseSensitive(child, "title")->valuestring);
+
+	cJSON* authors = cJSON_GetObjectItemCaseSensitive(child, "author_name");
+	printf("Author(s): ");
+	if (cJSON_IsArray(authors)) {
+		cJSON* authorarr = authors->child;
+		while (NULL != authorarr->next) {
+			printf("%s, ", authorarr->valuestring);
+			authorarr = authorarr->next;
+		}
+		printf("%s\n", authorarr->valuestring);
+	} else {
+		printf("Author(s): %s\n", authors->valuestring);
+	}
+
+	printf("Year of Publication: %d\n", cJSON_GetObjectItemCaseSensitive(child, "publish_year")->child->valueint);
+	printf("Page length: %d\n", cJSON_GetObjectItemCaseSensitive(child, "number_of_pages_median")->valueint);
+}
+
+int main(int argc, char* argv[])
+{
+	char isbn_buf[14];
+	CURLcode res;
+
+	if (2 != argc) {
+		printf("Usage: isbn [isbn]\n");
+		return EXIT_FAILURE;
+	}
+
+	/**
+	 * We must initialize cURL
+	 */
+	curl_global_init(CURL_GLOBAL_ALL);
+
+	/**
+	 * Grab the ISBN from argv
+	 */
+	snprintf(isbn_buf, 14, "%s", argv[1]);
+
+	/**
+	 * Setup the output string
+	 */
+	string get_output;
+	init_string(&get_output);
+
+	/**
+	 *  Perform the get request
+	 */ res = perform_book_get(isbn_buf, &get_output);
+	if (0 != res) {
+		fprintf(stderr, "Failed to perform the get request!\n");
+		return EXIT_FAILURE;
+	}
+
+	/**
+	 * Now we want to parse the JSON input
+	 */
+	parse_json(&get_output);
+
+	/**
+	 * We need to free this string
+	 */
+	free(get_output.buf);
+
+
+	return 0;
+}

test.c

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+#include <string.h>
+#include <stdio.h>
+
+int main(void)
+{
+	char* x = "Hello, ";
+	char* y = "world!";
+
+	size_t out_len = strlen(x) + strlen(y) + 1;
+	char out[out_len];
+	snprintf(out, out_len, "%s%s", x, y);
+	puts(out);
+	return 0;
+}