library api: tpax_file_create_tmpfs_snapshot(): initial implementation.

1 files changed, 133 insertions, 0 deletions

diff --git a/src/logic/tpax_file_create_tmpfs_snapshot.c b/src/logic/tpax_file_create_tmpfs_snapshot.c
new file mode 100644
index 0000000..3bb48b7
--- /dev/null
+++ b/src/logic/tpax_file_create_tmpfs_snapshot.c
@@ -0,0 +1,133 @@
+/******************************************************/
+/*  tpax: a topological pax implementation            */
+/*  Copyright (C) 2020  Z. Gilboa                     */
+/*  Released under GPLv2 and GPLv3; see COPYING.TPAX. */
+/******************************************************/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <sys/stat.h>
+
+#include <tpax/tpax.h>
+#include <tpax/tpax_specs.h>
+#include "tpax_driver_impl.h"
+#include "tpax_tmpfile_impl.h"
+#include "tpax_errinfo_impl.h"
+
+#ifndef ssizeof
+#define ssizeof(x) (ssize_t)(sizeof(x))
+#endif
+
+int tpax_file_create_tmpfs_snapshot(
+	const struct tpax_driver_ctx *  dctx,
+	const char *                    path,
+	const struct stat *             srcst)
+{
+	int          fdsrc;
+	int          fdtmp;
+	char *       ch;
+	ssize_t      nread;
+	ssize_t      nbytes;
+	ssize_t      ret;
+	void *       buf;
+	size_t       buflen;
+	struct stat  dstst;
+	char         sbuf[2048];
+
+	/* record errors */
+	tpax_driver_set_ectx(
+		dctx,0,path);
+
+	/* tmpfile */
+	if ((fdtmp = tpax_tmpfile()) < 0)
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	/* buffer */
+	if (!(buf = tpax_get_driver_anon_map_addr(dctx,&buflen))) {
+		buf    = sbuf;
+		buflen = sizeof(sbuf);
+	}
+
+	/* open */
+	fdsrc = openat(
+		tpax_driver_fdcwd(dctx),path,
+		O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+
+	if (fdsrc < 0) {
+		close(fdtmp);
+		return TPAX_SYSTEM_ERROR(dctx);
+	}
+
+	/* stat compare */
+	if ((fstat(fdsrc,&dstst)) < 0) {
+		close(fdsrc);
+		close(fdtmp);
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	} else if (tpax_stat_compare(srcst,&dstst)) {
+		close(fdsrc);
+		close(fdtmp);
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
+	}
+
+	/* read/write loop */
+	for (nread=0; nread<srcst->st_size; ) {
+		nbytes = read(fdsrc,buf,buflen);
+
+		while ((nbytes < 0) && (errno == EINTR))
+			nbytes = read(fdsrc,buf,buflen);
+
+		if (nbytes < 0) {
+			close(fdsrc);
+			close(fdtmp);
+			return TPAX_SYSTEM_ERROR(dctx);
+
+		} else if (nbytes == 0) {
+			close(fdsrc);
+			close(fdtmp);
+			return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR);
+
+		} else {
+			nread += nbytes;
+		}
+
+		for (ch=buf; nbytes; ch+=ret) {
+			ret = write(fdtmp,ch,nbytes);
+
+			while ((ret < 0) && (errno == EINTR))
+				ret = write(fdtmp,ch,nbytes);
+
+			if (ret < 0) {
+				close(fdsrc);
+				close(fdtmp);
+				return TPAX_SYSTEM_ERROR(dctx);
+
+			} else {
+				nbytes -= ret;
+			}
+		}
+	}
+
+	/* stat compare */
+	if ((fstat(fdsrc,&dstst)) < 0) {
+		close(fdsrc);
+		close(fdtmp);
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	} else if (tpax_stat_compare(srcst,&dstst)) {
+		close(fdsrc);
+		close(fdtmp);
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
+	}
+
+	/* yay */
+	close(fdsrc);
+
+	return fdtmp;
+}