library api: tpax_file_create_memory_snapshot(): initial implementation.

4 files changed, 109 insertions, 0 deletions

diff --git a/include/tpax/tpax.h b/include/tpax/tpax.h
index c39f721..8d6183b 100644
--- a/include/tpax/tpax.h
+++ b/include/tpax/tpax.h
@@ -66,6 +66,8 @@ enum tpax_custom_error {
 	TPAX_ERR_NULL_CONTEXT,
 	TPAX_ERR_BAD_DATA,
 	TPAX_ERR_FORBIDDEN_PATH,
+	TPAX_ERR_FILE_CHANGED,
+	TPAX_ERR_REGION_SIZE,
 	TPAX_ERR_CAP,
 };
 
@@ -161,6 +163,9 @@ tpax_api int  tpax_output_error_vector  (const struct tpax_driver_ctx *);
 tpax_api int  tpax_init_ustar_header    (const struct tpax_driver_ctx *, const char *, const struct stat *,
                                          const char *, struct tpax_ustar_header *);
 
+tpax_api int  tpax_file_create_memory_snapshot  (const struct tpax_driver_ctx *, const char *,
+                                                 const struct stat *, void *);
+
 /* package info */
 tpax_api const struct tpax_source_version * tpax_source_version(void);
 
diff --git a/project/common.mk b/project/common.mk
index 14d6ec8..da9fa26 100644
--- a/project/common.mk
+++ b/project/common.mk
@@ -5,6 +5,7 @@ API_SRCS = \
 	src/helper/tpax_path_copy.c \
 	src/helper/tpax_stat_compare.c \
 	src/logic/tpax_init_ustar_header.c \
+	src/logic/tpax_file_create_memory_snapshot.c \
 	src/output/tpax_output_error.c \
 	src/skin/tpax_skin_default.c \
 
diff --git a/src/logic/tpax_file_create_memory_snapshot.c b/src/logic/tpax_file_create_memory_snapshot.c
new file mode 100644
index 0000000..7db21ea
--- /dev/null
+++ b/src/logic/tpax_file_create_memory_snapshot.c
@@ -0,0 +1,101 @@
+/******************************************************/
+/*  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_errinfo_impl.h"
+
+#ifndef ssizeof
+#define ssizeof(x) (ssize_t)(sizeof(x))
+#endif
+
+int tpax_file_create_memory_snapshot(
+	const struct tpax_driver_ctx *  dctx,
+	const char *                    path,
+	const struct stat *             srcst,
+	void *                          addr)
+{
+	int          fd;
+	char *       ch;
+	char *       cap;
+	ssize_t      nread;
+	struct stat  dstst;
+
+	/* record errors */
+	tpax_driver_set_ectx(
+		dctx,0,path);
+
+	/* memory snapshot internal limit */
+	if (srcst->st_size >= 0x80000000)
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_REGION_SIZE);
+
+	/* open */
+	fd = openat(
+		tpax_driver_fdcwd(dctx),path,
+		O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+
+	if (fd < 0)
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	/* stat compare */
+	if ((fstat(fd,&dstst)) < 0) {
+		close(fd);
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	} else if (tpax_stat_compare(srcst,&dstst)) {
+		close(fd);
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
+	}
+
+	/* read loop */
+	ch  = addr;
+	cap = &ch[srcst->st_size];
+
+	while (ch < cap) {
+		nread = read(fd,ch,cap-ch);
+
+		while ((nread < 0) && (errno == EINTR))
+			nread = read(fd,ch,cap-ch);
+
+		if (nread < 0) {
+			close(fd);
+			return TPAX_SYSTEM_ERROR(dctx);
+
+		} else if (nread == 0) {
+			close(fd);
+			return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR);
+
+		} else {
+			ch += nread;
+		}
+	}
+
+	/* stat compare */
+	if ((fstat(fd,&dstst)) < 0) {
+		close(fd);
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	} else if (tpax_stat_compare(srcst,&dstst)) {
+		close(fd);
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
+	}
+
+	/* yay */
+	close(fd);
+
+	return 0;
+}
diff --git a/src/output/tpax_output_error.c b/src/output/tpax_output_error.c
index 69c4938..de09f21 100644
--- a/src/output/tpax_output_error.c
+++ b/src/output/tpax_output_error.c
@@ -26,6 +26,8 @@ static const char * const tpax_error_strings[TPAX_ERR_CAP] = {
 	[TPAX_ERR_FLEE_ERROR]      = "flees and bugs and cats and mice",
 	[TPAX_ERR_NULL_CONTEXT]    = "null driver or unit context",
 	[TPAX_ERR_BAD_DATA]        = "corrupt or wrong daata",
+	[TPAX_ERR_FILE_CHANGED]    = "file has changed",
+	[TPAX_ERR_REGION_SIZE]     = "file too large for a memory snapshot",
 };
 
 static const char * tpax_output_error_header(const struct tpax_error_info * erri)