Networking rework (#240)

* Began refactoring http_get. Still a few cases to handle, but it works.

* Introduced error enum; handle error 406; handle a misbehaving server; redirect_url leaked memory (L888)

* Allowed calls to http_get to pass NULL as acceptable_mime_types

* Removed status_code from header struct; eventually planning to move most of parse_header's logic back to http_get, so this makes sense

* Moved some more logic back into http_get
Note: currently behaves weirdly with some QR codes, including but probably not limited to ones pointing to TinyURL.

* Handle redirects correctly; other rearrangements

* Formatting

* Handle HTTP 303 See Other correctly

* Removed "Download failed" error in camera.c due to all related failures being handled in http_get

* Fixed missing loading bar; started working on unchunked download

* Added unchunked download

* Reintroduced the download progress bar, rolled back to always doing chunked download

* URL length caps at 2083 chars

* Slightly more efficient

* Correctly handle incorrect filesize header
TODO: reorder clauses to remove the goto?

* Fixed illegal characters, removed unnecessary logic (technically a regression, as we always have to realloc now)

* Finally finished up status code handling. Fixed a memory leak when the server fails conneg.

include/remote.h

@@ -52,6 +52,6 @@
 #define CACHE_PATH_FORMAT            "/3ds/"  APP_TITLE  "/cache/%"  JSON_INTEGER_FORMAT
 
 bool themeplaza_browser(EntryMode mode);
-u32 http_get(const char *url, char ** filename, char ** buf, InstallType install_type);
+u32 http_get(const char *url, char ** filename, char ** buf, InstallType install_type, const char *mime_type);
 
 #endif

source/camera.c

@@ -229,7 +229,7 @@ void update_qr(qr_data *data)
             draw_install(INSTALL_DOWNLOAD);
             char * zip_buf = NULL;
             char * filename = NULL;
-            u32 zip_size = http_get((char*)scan_data.payload, &filename, &zip_buf, INSTALL_DOWNLOAD);
+            u32 zip_size = http_get((char*)scan_data.payload, &filename, &zip_buf, INSTALL_DOWNLOAD, "application/zip");
 
             if(zip_size != 0)
             {
@@ -288,19 +288,17 @@ void update_qr(qr_data *data)
                     }
                     else
                     {
+                        // TODO: handle more elegantly
                         throw_error("Zip downloaded is neither\na splash nor a theme.", ERROR_LEVEL_WARNING);
                     }
                 }
                 else
                 {
+                    // TODO: marked for deletion
                     throw_error("File downloaded isn't a zip.", ERROR_LEVEL_WARNING);
                 }
                 free(zip_buf);
             }
-            else
-            {
-                throw_error("Download failed.", ERROR_LEVEL_WARNING);
-            }
 
             free(filename);
         }   

source/remote.c

@@ -128,7 +128,7 @@ static C2D_Image * load_remote_smdh(Entry_s * entry, bool ignore_cache)
         smdh_buf = NULL;
         char * api_url = NULL;
         asprintf(&api_url, THEMEPLAZA_SMDH_FORMAT, entry->tp_download_id);
-        smdh_size = http_get(api_url, NULL, &smdh_buf, INSTALL_NONE);
+        smdh_size = http_get(api_url, NULL, &smdh_buf, INSTALL_NONE, "application/octet-stream");
         free(api_url);
     }
 
@@ -205,7 +205,7 @@ static void load_remote_list(Entry_List_s * list, json_int_t page, EntryMode mod
     char * page_json = NULL;
     char * api_url = NULL;
     asprintf(&api_url, THEMEPLAZA_PAGE_FORMAT, page, mode + 1, list->tp_search);
-    u32 json_len = http_get(api_url, NULL, &page_json, INSTALL_NONE);
+    u32 json_len = http_get(api_url, NULL, &page_json, INSTALL_NONE, "application/json");
     free(api_url);
 
     if (json_len)
@@ -228,7 +228,8 @@ static void load_remote_list(Entry_List_s * list, json_int_t page, EntryMode mod
                     list->tp_page_count = json_integer_value(value);
                 else if (json_is_array(value) && !strcmp(key, THEMEPLAZA_JSON_PAGE_IDS))
                     load_remote_entries(list, value, ignore_cache, loading_screen);
-                else if(json_is_string(value) && !strcmp(key, THEMEPLAZA_JSON_ERROR_MESSAGE) && !strcmp(json_string_value(value), THEMEPLAZA_JSON_ERROR_MESSAGE_NOT_FOUND))
+                else if (json_is_string(value) && !strcmp(key, THEMEPLAZA_JSON_ERROR_MESSAGE)
+                    && !strcmp(json_string_value(value), THEMEPLAZA_JSON_ERROR_MESSAGE_NOT_FOUND))
                     throw_error("No results for this search.", ERROR_LEVEL_WARNING);
             }
         }
@@ -244,6 +245,7 @@ static void load_remote_list(Entry_List_s * list, json_int_t page, EntryMode mod
 }
 
 static u16 previous_path_preview[0x106] = { 0 };
+
 static bool load_remote_preview(Entry_s * entry, C2D_Image * preview_image, int * preview_offset)
 {
     bool not_cached = true;
@@ -265,7 +267,7 @@ static bool load_remote_preview(Entry_s * entry, C2D_Image* preview_image, int *
 
         draw_install(INSTALL_LOADING_REMOTE_PREVIEW);
 
-        preview_size = http_get(preview_url, NULL, &preview_png, INSTALL_LOADING_REMOTE_PREVIEW);
+        preview_size = http_get(preview_url, NULL, &preview_png, INSTALL_LOADING_REMOTE_PREVIEW, "image/png");
         free(preview_url);
     }
 
@@ -292,6 +294,7 @@ static bool load_remote_preview(Entry_s * entry, C2D_Image* preview_image, int *
 }
 
 static u16 previous_path_bgm[0x106] = { 0 };
+
 static void load_remote_bgm(Entry_s * entry)
 {
     if (!memcmp(&previous_path_bgm, entry->path, 0x106 * sizeof(u16))) return;
@@ -309,7 +312,7 @@ static void load_remote_bgm(Entry_s * entry)
 
         draw_install(INSTALL_LOADING_REMOTE_BGM);
 
-        bgm_size = http_get(bgm_url, NULL, &bgm_ogg, INSTALL_LOADING_REMOTE_BGM);
+        bgm_size = http_get(bgm_url, NULL, &bgm_ogg, INSTALL_LOADING_REMOTE_BGM, "application/ogg, audio/ogg");
         free(bgm_url);
 
         u16 path[0x107] = { 0 };
@@ -332,7 +335,7 @@ static void download_remote_entry(Entry_s * entry, EntryMode mode)
     char * zip_buf = NULL;
     char * filename = NULL;
     draw_install(INSTALL_DOWNLOAD);
-    u32 zip_size = http_get(download_url, &filename, &zip_buf, INSTALL_DOWNLOAD);
+    u32 zip_size = http_get(download_url, &filename, &zip_buf, INSTALL_DOWNLOAD, "application/zip");
     free(download_url);
 
     char path_to_file[0x107] = { 0 };
@@ -349,7 +352,8 @@ static void download_remote_entry(Entry_s * entry, EntryMode mode)
     free(zip_buf);
 }
 
-static SwkbdCallbackResult jump_menu_callback(void* page_number, const char** ppMessage, const char* text, size_t textlen)
+static SwkbdCallbackResult
+jump_menu_callback(void * page_number, const char ** ppMessage, const char * text, size_t textlen)
 {
     (void)textlen;
     int typed_value = atoi(text);
@@ -374,11 +378,13 @@ static void jump_menu(Entry_List_s * list)
 
     SwkbdState swkbd;
 
-    sprintf(numbuf, "%"  JSON_INTEGER_FORMAT, list->tp_page_count);
+    sprintf(numbuf, "%"
+    JSON_INTEGER_FORMAT, list->tp_page_count);
     int max_chars = strlen(numbuf);
     swkbdInit(&swkbd, SWKBD_TYPE_NUMPAD, 2, max_chars);
 
-    sprintf(numbuf, "%"  JSON_INTEGER_FORMAT, list->tp_current_page);
+    sprintf(numbuf, "%"
+    JSON_INTEGER_FORMAT, list->tp_current_page);
     swkbdSetInitialText(&swkbd, numbuf);
 
     sprintf(numbuf, "Which page do you want to jump to?");
@@ -720,171 +726,327 @@ bool themeplaza_browser(EntryMode mode)
     return downloaded;
 }
 
-u32 http_get(const char *url, char ** filename, char ** buf, InstallType install_type)
+typedef struct header
+{
+    char * filename; // allocated in parse_header; if NULL, this is user-provided
+    u32 file_size; // if == 0, fall back to chunked read
+} header;
+
+typedef enum ParseResult
+{
+    SUCCESS, // 200/203 (203 indicates a successful request with a transformation applied by a proxy)
+    REDIRECT, // 301/302/303/307/308
+    HTTPC_ERROR,
+    SERVER_IS_MISBEHAVING,
+    NO_FILENAME, // provisional
+    HTTP_UNAUTHORIZED = 401,
+    HTTP_FORBIDDEN = 403,
+    HTTP_NOT_FOUND = 404,
+    HTTP_UNACCEPTABLE = 406, // like 204, usually doesn't happen
+    HTTP_PROXY_UNAUTHORIZED = 407,
+    HTTP_GONE = 410,
+    HTTP_URI_TOO_LONG = 414,
+    HTTP_IM_A_TEAPOT = 418, // Note that a combined coffee/tea pot that is temporarily out of coffee should instead return 503.
+    HTTP_UPGRADE_REQUIRED = 426, // the 3DS doesn't support HTTP/2, so we can't upgrade - inform and return
+    HTTP_LEGAL_REASONS = 451,
+    HTTP_INTERNAL_SERVER_ERROR = 500,
+    HTTP_BAD_GATEWAY = 502,
+    HTTP_SERVICE_UNAVAILABLE = 503,
+    HTTP_GATEWAY_TIMEOUT = 504,
+} ParseResult;
+
+// the good paths for this function return SUCCESS or REDIRECT;
+// all other paths are failures
+static ParseResult parse_header(struct header * out, httpcContext * context, bool get_filename, const char * mime)
+{
+    // status code
+    u32 status_code;
+
+    if (httpcGetResponseStatusCode(context, &status_code))
+    {
+        DEBUG("httpcGetResponseStatusCode\n");
+        return HTTPC_ERROR;
+    }
+
+    DEBUG("HTTP %lu\n", status_code);
+    switch (status_code)
+    {
+    case 301:
+    case 302:
+    case 307:
+    case 308:
+        return REDIRECT;
+    case 200:
+    case 203:
+        break;
+    default:
+        return (ParseResult)status_code;
+    }
+
+    char * content_buf = calloc(1024, sizeof(char));
+
+    // Content-Type
+
+    if (mime)
+    {
+        httpcGetResponseHeader(context, "Content-Type", content_buf, 1024);
+        if (!strstr(mime, content_buf))
+        {
+            free(content_buf);
+            return SERVER_IS_MISBEHAVING;
+        }
+    }
+
+    // Content-Length
+
+    if (httpcGetDownloadSizeState(context, NULL, &out->file_size))
+    {
+        DEBUG("httpcGetDownloadSizeState\n");
+        return HTTPC_ERROR; // no need to free, program dies anyway
+    }
+
+    // Content-Disposition
+
+    if (get_filename)
+    {
+        if (httpcGetResponseHeader(context, "Content-Disposition", content_buf, 1024))
+        {
+            free(content_buf);
+            DEBUG("httpcGetResponseHeader\n");
+            return HTTPC_ERROR;
+        }
+
+        // content_buf: Content-Disposition: attachment; ... filename=<filename>;? ...
+
+        char * filename = strstr(content_buf, "filename="); // filename=<filename>;? ...
+        if (!filename)
+        {
+            free(content_buf);
+            return NO_FILENAME;
+        }
+
+        filename = strpbrk(filename, "=") + 1; // <filename>;?
+        char * end = strpbrk(filename, ";");
+        if (end)
+            *end = '\0'; // <filename>
+
+        if (filename[0] == '"')
+            // safe to assume the filename is quoted
+        {
+            filename[strlen(filename) - 1] = '\0';
+            filename++;
+        }
+
+        char * illegal_char;
+        // filter out characters illegal in FAT32 filenames
+        while ((illegal_char = strpbrk(filename, "><\"?;:/\\+,.|[=]")))
+            *illegal_char = '-';
+
+        out->filename = malloc(strlen(filename) + 1);
+        strcpy(out->filename, filename);
+        DEBUG("%s\n", out->filename);
+    }
+    return SUCCESS;
+}
+
+#define ZIP_NOT_AVAILABLE "ZIP not found at this URL\nIf you believe this is an error, please\ncontact the site administrator"
+
+/*
+ * call example: written = http_get("url", &filename, &buffer_to_download_to, INSTALL_DOWNLOAD, "application/json");
+ */
+u32 http_get(const char * url, char ** filename, char ** buf, InstallType install_type, const char * acceptable_mime_types)
 {
     Result ret;
     httpcContext context;
-    char *new_url = NULL;
+    char redirect_url[0x824] = {0};
-    u32 status_code;
+    char new_url[0x824] = {0};
-    u32 content_size = 0;
-    u32 read_size = 0;
-    u32 size = 0;
-    char *last_buf;
 
-    do {
+    struct header _header = {};
+
+    DEBUG("Original URL: %s\n", url);
+
+redirect: // goto here if we need to redirect
     ret = httpcOpenContext(&context, HTTPC_METHOD_GET, url, 1);
     if (ret != 0)
     {
         httpcCloseContext(&context);
-            if (new_url != NULL) free(new_url);
         DEBUG("httpcOpenContext %.8lx\n", ret);
         return 0;
     }
-        ret = httpcSetSSLOpt(&context, SSLCOPT_DisableVerify); // should let us do https
+
-        ret = httpcSetKeepAlive(&context, HTTPC_KEEPALIVE_ENABLED);
+    httpcSetSSLOpt(&context, SSLCOPT_DisableVerify); // should let us do https
-        ret = httpcAddRequestHeaderField(&context, "User-Agent", USER_AGENT);
+    httpcSetKeepAlive(&context, HTTPC_KEEPALIVE_ENABLED);
-        ret = httpcAddRequestHeaderField(&context, "Connection", "Keep-Alive");
+    httpcAddRequestHeaderField(&context, "User-Agent", USER_AGENT);
+    httpcAddRequestHeaderField(&context, "Connection", "Keep-Alive");
+    if (acceptable_mime_types)
+        httpcAddRequestHeaderField(&context, "Accept", acceptable_mime_types);
 
     ret = httpcBeginRequest(&context);
     if (ret != 0)
     {
         httpcCloseContext(&context);
-            if (new_url != NULL) free(new_url);
         DEBUG("httpcBeginRequest %.8lx\n", ret);
         return 0;
     }
 
-        ret = httpcGetResponseStatusCode(&context, &status_code);
+    ParseResult parse = parse_header(&_header, &context, (bool)filename, acceptable_mime_types);
-        if(ret!=0){
+    switch (parse)
-            httpcCloseContext(&context);
-            if(new_url!=NULL) free(new_url);
-            DEBUG("httpcGetResponseStatusCode\n");
-            return 0;
-        }
-
-        if ((status_code >= 301 && status_code <= 303) || (status_code >= 307 && status_code <= 308))
     {
-            if (new_url == NULL) new_url = malloc(0x1000);
+    case NO_FILENAME:
-            ret = httpcGetResponseHeader(&context, "Location", new_url, 0x1000);
+    case SUCCESS:
+        break;
+    case REDIRECT:
+        httpcGetResponseHeader(&context, "Location", redirect_url, 0x824);
+        httpcCloseContext(&context);
+        if (*redirect_url == '/') // if relative URL
+        {
+            strcpy(new_url, url);
+            // this is good code, i promise
+            *(strchr(strchr(strchr(new_url, '/') + 1, '/') + 1, '/')) = '\0';
+            strncat(new_url, redirect_url, 0x824 - strlen(new_url));
             url = new_url;
-            httpcCloseContext(&context);
         }
-    } while ((status_code >= 301 && status_code <= 303) || (status_code >= 307 && status_code <= 308));
+        else
-
-    if (status_code != 200)
         {
-        httpcCloseContext(&context);
+            url = redirect_url;
-        if (new_url != NULL) free(new_url);
-        DEBUG("status_code, %lu\n", status_code);
-        return 0;
         }
-
+        DEBUG("HTTP Redirect: %s %s\n", new_url, *redirect_url == '/' ? "relative" : "absolute");
-    ret = httpcGetDownloadSizeState(&context, NULL, &content_size);
+        goto redirect;
-    if (ret != 0)
+    case HTTP_UNACCEPTABLE:
+        DEBUG("HTTP 406 Unacceptable; Accept: %s\n", acceptable_mime_types);
+        throw_error(ZIP_NOT_AVAILABLE, ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case SERVER_IS_MISBEHAVING:
+        DEBUG("Server is misbehaving (provided resource with incorrect MIME)\n");
+        throw_error(ZIP_NOT_AVAILABLE, ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTPC_ERROR:
+        DEBUG("httpc error\n");
+        throw_error("Error in HTTPC sysmodule.\nIf you are seeing this, please contact an Anemone developer\non the ThemePlaza Discord.", ERROR_LEVEL_ERROR);
+        quit = true;
+        return httpcCloseContext(&context);
+    case HTTP_NOT_FOUND:
+    case HTTP_GONE:
+        // TODO: check if we're looking at a TP URL, if we are, suggest that it might be missing
+        const char * http_error = parse == HTTP_NOT_FOUND ? "404 Not Found" : "410 Gone";
+        DEBUG("HTTP %s; URL: %s\n", http_error, url);
+        char err_buf[0x69];
+        snprintf(err_buf, 0x69, "HTTP %s\nCheck that the URL is correct.", http_error);
+        throw_error(err_buf, ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_UNAUTHORIZED:
+    case HTTP_FORBIDDEN:
+    case HTTP_PROXY_UNAUTHORIZED:
+        DEBUG("HTTP %u: device not authenticated\n", parse);
+        char err_buf[0x69];
+        snprintf(err_buf, 0x69, "HTTP %s\nContact the site administrator.", parse == HTTP_UNAUTHORIZED
+            ? "401 Unauthorized"
+            : parse == HTTP_FORBIDDEN
+            ? "403 Forbidden"
+            : "407 Proxy Authentication Required");
+        throw_error(err_buf, ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_URI_TOO_LONG:
+        DEBUG("HTTP 414; URL is too long, maybe too many redirects?\n");
+        throw_error("HTTP 414 URI Too Long\nThe QR code points to a really long URL.\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_IM_A_TEAPOT:
+        DEBUG("HTTP 418 I'm a teapot\n");
+        throw_error("HTTP 418 I'm a teapot\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_UPGRADE_REQUIRED:
+        DEBUG("HTTP 426; HTTP/2 required\n");
+        throw_error("HTTP 426 Upgrade Required\nThe 3DS does not support this website.\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_LEGAL_REASONS:
+        DEBUG("HTTP 451; URL: %s\n", url);
+        throw_error("HTTP 451 Unavailable for Legal Reasons\nSome entity is preventing access\nto the host server for legal reasons.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_INTERNAL_SERVER_ERROR:
+        DEBUG("HTTP 500\n");
+        throw_error("HTTP 500 Internal Server Error\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_BAD_GATEWAY:
+        DEBUG("HTTP 502\n");
+        throw_error("HTTP 502 Bad Gateway\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_SERVICE_UNAVAILABLE:
+        DEBUG("HTTP 503\n");
+        throw_error("HTTP 503 Service Unavailable\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    case HTTP_GATEWAY_TIMEOUT:
+        DEBUG("HTTP 504\n");
+        throw_error("HTTP 504 Gateway Timeout\nContact the site administrator.", ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
+    default:
     {
-        httpcCloseContext(&context);
+        DEBUG("HTTP %u\n", parse);
-        if (new_url != NULL) free(new_url);
+        char err_buf[0x69];
-        DEBUG("httpcGetDownloadSizeState\n");
+        snprintf(err_buf, 0x69, "HTTP %u\nIf you believe this is unexpected, please\ncontact the site administrator.", parse);
-        return 0;
+        throw_error(err_buf, ERROR_LEVEL_WARNING);
+        return httpcCloseContext(&context);
     }
-
-    *buf = malloc(0x1000);
-    if (*buf == NULL)
-    {
-        httpcCloseContext(&context);
-        free(new_url);
-        DEBUG("malloc\n");
-        return 0;
     }
 
     if (filename)
     {
-        char *content_disposition = calloc(1024, sizeof(char));
+        if (parse != NO_FILENAME)
-        ret = httpcGetResponseHeader(&context, "Content-Disposition", content_disposition, 1024);
+            *filename = _header.filename;
-        if (ret != 0)
+        else
         {
-            free(content_disposition);
+            // TODO: swkbd stuff
-            free(new_url);
+            // needs to be heap allocated only because the call site is expected to free it
+            *filename = malloc(0x20);
+            sprintf(*filename, "tobesupplied.zip");
+        }
+    }
+
+    u32 chunk_size;
+    if (_header.file_size)
+        // the only reason we chunk this at all is for the download bar;
+        // in terms of efficiency, allocating the full size
+        // would avoid 3 reallocs whenever the server isn't lying
+        chunk_size = _header.file_size / 4;
+    else
+        chunk_size = 0x80000;
+
+    *buf = NULL;
+    char * new_buf;
+    u32 size = 0;
+    u32 read_size = 0;
+
+    do
+    {
+        new_buf = realloc(*buf, size + chunk_size);
+        if (new_buf == NULL)
+        {
+            httpcCloseContext(&context);
             free(*buf);
-            DEBUG("httpcGetResponseHeader\n");
+            DEBUG("realloc failed in http_get - file possibly too large?\n"); // TODO: report this?
             return 0;
         }
+        *buf = new_buf;
 
-        char * tok = strstr(content_disposition, "filename=");
+        // download exactly chunk_size bytes and toss them into buf.
-
+        // size contains the current offset into buf.
-        if(!(tok))
+        ret = httpcDownloadData(&context, (u8*)(*buf) + size, chunk_size, &read_size);
-        {
-            free(content_disposition);
-            free(new_url);
-            free(*buf);
-            throw_error("Target is not valid!", ERROR_LEVEL_WARNING);
-            DEBUG("filename\n");
-            return 0;
-        }
-
-        tok += sizeof("filename=") - 1;
-        if(ispunct((int)*tok))
-        {
-            tok++;
-        }
-        char* last_char = tok + strlen(tok) - 1;
-        if(ispunct((int)*last_char))
-        {
-            *last_char = '\0';
-        }
-
-        char *illegal_characters = "\"?;:/\\+";
-        for (size_t i = 0; i < strlen(tok); i++)
-        {
-            for (size_t n = 0; n < strlen(illegal_characters); n++)
-            {
-                if ((tok)[i] == illegal_characters[n])
-                {
-                    (tok)[i] = '-';
-                }
-            }
-        }
-
-        *filename = calloc(1024, sizeof(char));
-        strcpy(*filename, tok);
-        free(content_disposition);
-    }
-
-    do {
-        ret = httpcDownloadData(&context, (*(u8**)buf) + size, 0x1000, &read_size);
         size += read_size;
 
-        if(content_size && install_type != INSTALL_NONE)
+        if (_header.file_size && install_type != INSTALL_NONE)
-            draw_loading_bar(size, content_size, install_type);
+            draw_loading_bar(size, _header.file_size, install_type);
-
-        if (ret == (s32)HTTPC_RESULTCODE_DOWNLOADPENDING)
-        {
-            last_buf = *buf;
-            *buf = realloc(*buf, size + 0x1000);
-            if (*buf == NULL)
-            {
-                httpcCloseContext(&context);
-                free(new_url);
-                free(last_buf);
-                DEBUG("NULL\n");
-                return 0;
-            }
-        }
     } while (ret == (s32)HTTPC_RESULTCODE_DOWNLOADPENDING);
+    httpcCloseContext(&context);
 
-    last_buf = *buf;
+    // shrink to size
-    *buf = realloc(*buf, size);
+    new_buf = realloc(*buf, size);
-    if (*buf == NULL)
+    if (new_buf == NULL)
     {
         httpcCloseContext(&context);
-        free(new_url);
+        free(*buf);
-        free(last_buf);
+        DEBUG("shrinking realloc failed\n"); // 何？
-        DEBUG("realloc\n");
         return 0;
     }
-
+    *buf = new_buf;
-    httpcCloseContext(&context);
-    free(new_url);
 
     DEBUG("size: %lu\n", size);
     return size;