Introduce xbps_binpkg_get_file_into_fd() and use it for xbps-query(8) --cat.

This allows you to print to stdout any file stored in a binary package,
locally or remotely!

$ xbps-query -R --cat=/usr/bin/ls coreutils > ls
$ file ls
ls: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=7a195fc46d1d5cdca32bfccd3b30f81784e342ed, stripped
$

bin/xbps-query/show-info-files.c

@@ -311,7 +311,8 @@ int
 repo_cat_file(struct xbps_handle *xhp, const char *pkg, const char *file)
 {
 	xbps_dictionary_t pkgd;
-	char *url, *buf;
+	char *url;
+	int rv;
 
 	pkgd = xbps_rpool_get_pkg(xhp, pkg);
 	if (pkgd == NULL)
@@ -322,14 +323,9 @@ repo_cat_file(struct xbps_handle *xhp, const char *pkg, const char *file)
 		return EINVAL;
 
 	xbps_dbg_printf(xhp, "matched pkg at %s\n", url);
-	buf = xbps_binpkg_get_file(url, file);
+	rv = xbps_binpkg_get_file_into_fd(url, file, STDOUT_FILENO);
 	free(url);
-	if (buf == NULL)
+	return rv;
-		return ENOENT;
-
-	printf("%s", buf);
-	free(buf);
-	return 0;
 }
 
 int

include/xbps.h.in

@@ -48,7 +48,7 @@
  *
  * This header documents the full API for the XBPS Library.
  */
-#define XBPS_API_VERSION	"20141117"
+#define XBPS_API_VERSION	"20141117-1"
 
 #ifndef XBPS_VERSION
  #define XBPS_VERSION		"UNSET"
@@ -1141,6 +1141,20 @@ int xbps_transaction_commit(struct xbps_handle *xhp);
  * and errno is set appropiately.
  */
 char *xbps_binpkg_get_file(const char *url, const char *fname);
+
+/**
+ * Returns a file stored in a binary package locally or
+ * remotely as specified in the url \a url and stores it into the
+ * file descriptor \a fd.
+ *
+ * @param[in] url Full URL to binary package file (local or remote path).
+ * @param[in] fname File name to match.
+ * @param[in] fd An open file descriptor to put the file into.
+ *
+ * @return 0 on success, an errno value otherwise.
+ */
+int xbps_binpkg_get_file_into_fd(const char *url, const char *fname, int fd);
+
 /**
  * Internalizes a plist file in a binary package file stored locally or
  * remotely as specified in the url \a url.

lib/plist_fetch.c

@@ -168,6 +168,39 @@ xbps_binpkg_get_file(const char *url, const char *fname)
 	return buf;
 }
 
+int
+xbps_binpkg_get_file_into_fd(const char *url, const char *fname, int fd)
+{
+	struct archive *a;
+	struct archive_entry *entry;
+	int rv = 0;
+
+	assert(url);
+	assert(fname);
+	assert(fd != -1);
+
+	if ((a = open_archive(url)) == NULL)
+		return EINVAL;
+
+	while ((archive_read_next_header(a, &entry)) == ARCHIVE_OK) {
+		const char *bfile;
+
+		bfile = archive_entry_pathname(entry);
+		bfile++; /* skip first dot */
+		if (strcmp(bfile, fname) == 0) {
+			rv = archive_read_data_into_fd(a, fd);
+			if (rv != 0)
+				rv = archive_errno(a);
+
+			break;
+		}
+		archive_read_data_skip(a);
+	}
+	archive_read_finish(a);
+
+	return rv;
+}
+
 xbps_dictionary_t
 xbps_binpkg_get_plist(const char *url, const char *plistf)
 {