Handle http:// torrent urls

Makefile

@@ -1,4 +1,5 @@
 MultiThread = Yes
+HttpTorrent = Yes
 InstallPrefix = /usr/local/bin
 
 PROGNAME = torrent-verify
@@ -8,10 +9,15 @@ CPPFLAGS = -DPROGRAM_NAME='"$(PROGNAME)"' -DBUILD_INFO \
 		   -DBUILD_HASH="\"`git rev-parse --abbrev-ref HEAD` -> `git rev-parse --short HEAD`\"" -DBUILD_DATE="\"`date -I`\""
 
 ifeq ($(MultiThread), Yes)
-CFLAGS += -lpthread
+LDLIBS += -lpthread
 CPPFLAGS += -DMT
 endif
 
+ifeq ($(HttpTorrent), Yes)
+LDLIBS += -lcurl
+CPPFLAGS += -DHTTP_TORRENT=1
+endif
+
 SOURCE =  $(wildcard subm/heapless-bencode/*.c) $(wildcard src/*.c)
 #OBJ = $(addsuffix .o,$(basename $(SOURCE)))
 OBJS = $(SOURCE:.c=.o)
@@ -25,7 +31,8 @@ uninstall:
 	rm -f -- $(InstallPrefix)/$(PROGNAME)
 
 $(PROGNAME): $(OBJS)
-	$(CC) -o $@ $+ $(CFLAGS) $(CPPFLAGS)
+	$(CC) -o $@ $+ $(CFLAGS) $(CPPFLAGS) $(LDLIBS)
+
 
 clean:
 	-rm -- $(OBJS) $(PROGNAME)

src/main.c

@@ -42,6 +42,9 @@ BUILD_HASH " (" BUILD_DATE ")\n"
 #ifdef MT
 "MultiThread support\n"
 #endif
+#ifdef HTTP_TORRENT
+"HTTP Torrent support\n"
+#endif
 #endif
 );
     exit(EXIT_SUCCESS);
@@ -55,7 +58,11 @@ int main(int argc, char** argv) {
         help();
 
     if (optind >= argc) {
-        fprintf(stderr, "Provide at least one torrent file\n");
+        fprintf(stderr, "Provide at least one torrent file"
+#ifdef HTTP_TORRENT
+                        " or an http link to a torrent file"
+#endif
+                        "\n");
         usage();
     }
     

src/metainfo.c

@@ -3,18 +3,30 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <stdint.h>
 
 #include "sha1.h"
 
+#ifdef HTTP_TORRENT
+#include <curl/curl.h>
+#endif
+
 /* 128 MiB */
 #define MAX_TORRENT_SIZE 128*1024*1024
 
+#ifdef HTTP_TORRENT
+struct http_metainfo {
+    int64_t c_size, max_size;
+    char *data;
+};
+#endif
+
 /* 
  * Read the file in memory, and return the pointer to it (which needs to be
  * freed) in out_contents and the size in out_size. If the file is too big,
  * fail. Returns 0 on success and an errno on fail.
  */
-static int metainfo_read(const char* path, char** out_contents, int* out_size) {
+static int metainfo_read_file(const char* path, char** out_contents, int* out_size) {
     int ret = 0;
     FILE* f = NULL;
     long size = 0;
@@ -67,6 +79,146 @@ end:
     return ret;
 }
 
+#ifdef HTTP_TORRENT
+static size_t metainfo_read_http_headercb(char *buf, size_t size, size_t n,
+        void *data) {
+    struct http_metainfo *h_meta = (struct http_metainfo*)data;
+    const char *cl_header = "content-length";
+    char *sep = memchr(buf, ':', size * n);
+
+    if (!sep || (sep - buf) != strlen(cl_header))
+        goto end;
+
+    if (strncmp(cl_header, buf, strlen(cl_header)) == 0) {
+        char *endp;
+        int64_t len;
+
+        sep += 2;
+        errno = 0;
+        len = strtoll(sep, &endp, 10);
+        if (sep != endp && errno == 0)
+            h_meta->max_size = len;
+    }
+    
+end:
+    return size * n;
+}
+
+static size_t metainfo_read_http_writecb(char *ptr, size_t size, size_t n,
+        void *data) {
+    struct http_metainfo *h_meta = (struct http_metainfo*)data;
+    size_t bytes = size * n;
+
+    if (h_meta->max_size >= MAX_TORRENT_SIZE)
+        goto fail; /* Stop processing if too large */
+
+    if (h_meta->max_size == -1) {
+        /* If no content-length, make a dinamic array */
+        h_meta->max_size = 0;
+    } else if (!h_meta->data) {
+        /* We have content-size, and we haven't alloced yet */
+        h_meta->data = malloc(h_meta->max_size);
+    }
+
+    size_t free_space = h_meta->max_size - h_meta->c_size;
+
+    if (bytes > free_space) {
+        while (bytes > free_space) {
+            if (h_meta->max_size == 0)
+                h_meta->max_size = 2048;
+
+            h_meta->max_size *= 2;
+            free_space = h_meta->max_size - h_meta->c_size;
+        }
+
+        void *n_data = realloc(h_meta->data, h_meta->max_size);
+        if (!n_data)
+            goto fail;
+
+        h_meta->data = n_data;
+    }
+
+    if (h_meta->c_size + bytes > MAX_TORRENT_SIZE)
+        goto fail;
+
+    memcpy(&h_meta->data[h_meta->c_size], ptr, bytes);
+    h_meta->c_size += bytes;
+
+    return bytes;
+
+fail:
+    if (h_meta->data)
+        free(h_meta->data);
+    return 0;
+}
+#endif
+
+/* 
+ * Download the file in memory, and return the pointer to it (which needs to be
+ * freed) in out_contents and the size in out_size. If the file is too big,
+ * fail. Returns 0 on success and an errno on fail.
+ */
+static int metainfo_read_http(const char* url, char** out_contents, int* out_size) {
+#ifdef HTTP_TORRENT
+    char errbuf[CURL_ERROR_SIZE];
+    CURL *curl = curl_easy_init();
+    CURLcode res;
+    struct http_metainfo h_meta = {
+        .c_size = 0,
+        .max_size = -1,
+        .data = NULL,
+    };
+
+    if (!curl) {
+        return -1; /* Not errno but eh */
+    }
+
+    curl_easy_setopt(curl, CURLOPT_HEADERDATA, &h_meta);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &h_meta);
+    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, metainfo_read_http_headercb);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, metainfo_read_http_writecb);
+    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errbuf);
+    curl_easy_setopt(curl, CURLOPT_URL, url);
+
+    res = curl_easy_perform(curl);
+
+    curl_easy_cleanup(curl);
+
+    if (res) {
+        fprintf(stderr, "libCurl error: %s\n", errbuf);
+        return res;
+    }
+
+    *out_contents = h_meta.data;
+    *out_size = h_meta.c_size; /* caller will free */
+
+    return 0;
+#else
+    __builtin_unreachable(); /* Could be better tbh */
+#endif
+}
+
+/* 
+ * Read/download the file in memory, and return the pointer to it (which needs to be
+ * freed) in out_contents and the size in out_size. If the file is too big,
+ * fail. Returns 0 on success and an errno on fail.
+ */
+static int metainfo_read(const char* path, char** out_contents, int* out_size) {
+#ifdef HTTP_TORRENT
+    const int has_http = 1;
+#else
+    const int has_http = 0;
+#endif
+
+    if (strncmp(path, "http", 4) == 0) {
+        if (!has_http)
+            return ENOPROTOOPT;
+        return metainfo_read_http(path, out_contents, out_size);
+    }
+
+    return metainfo_read_file(path, out_contents, out_size);
+}
+
 static int len_strcmp(const char* s1, int s1_len, const char* s2, int s2_len) {
     return (s1_len == s2_len) && (strncmp(s1, s2, s1_len) == 0);
 }
@@ -173,8 +325,8 @@ static int metainfo_parse(metainfo_t* metai, bencode_t* benc) {
 }
 
 int metainfo_create(metainfo_t* metai, const char* path) {
-    char* bytes;
+    char* bytes = NULL;
-    int size;
+    int size = 0;
     int ret = metainfo_read(path, &bytes, &size);
     if (ret) {
         fprintf(stderr, "Metafile reading failed: %s\n", \