diff --git a/include/tpax/tpax.h b/include/tpax/tpax.h
index 3514858..ac7745a 100644
--- a/include/tpax/tpax.h
+++ b/include/tpax/tpax.h
@@ -172,12 +172,12 @@ tpax_api int  tpax_output_error_record      (const struct tpax_driver_ctx *, con
 tpax_api int  tpax_meta_init_ustar_header   (const struct tpax_driver_ctx *, const char *, const struct stat *,
                                              const char *, struct tpax_ustar_header *);
 
-/* low-level api */
-tpax_api int  tpax_file_create_memory_snapshot  (const struct tpax_driver_ctx *, int, const char *,
-                                                 const struct stat *, void *);
+/* low-level interfaces */
+tpax_api int  tpax_io_create_memory_snapshot(const struct tpax_driver_ctx *, int, const char *,
+                                             const struct stat *, void *);
 
-tpax_api int  tpax_file_create_tmpfs_snapshot   (const struct tpax_driver_ctx *, int, const char *,
-                                                 const struct stat *);
+tpax_api int  tpax_io_create_tmpfs_snapshot (const struct tpax_driver_ctx *, int, const char *,
+                                             const struct stat *);
 
 /* package info */
 tpax_api const struct tpax_source_version * tpax_source_version(void);
diff --git a/project/common.mk b/project/common.mk
index 43297fb..a23c2ef 100644
--- a/project/common.mk
+++ b/project/common.mk
@@ -2,10 +2,10 @@ API_SRCS = \
 	src/driver/tpax_amain.c \
 	src/driver/tpax_driver_ctx.c \
 	src/driver/tpax_unit_ctx.c \
+	src/io/tpax_create_memory_snapshot.c \
+	src/io/tpax_create_tmpfs_snapshot.c \
 	src/logic/tpax_archive_append.c \
 	src/logic/tpax_archive_write.c \
-	src/logic/tpax_file_create_memory_snapshot.c \
-	src/logic/tpax_file_create_tmpfs_snapshot.c \
 	src/logic/tpax_queue_vector.c \
 	src/meta/tpax_init_ustar_header.c \
 	src/output/tpax_output_error.c \
diff --git a/project/tree.mk b/project/tree.mk
index 90a5470..affd4ba 100644
--- a/project/tree.mk
+++ b/project/tree.mk
@@ -1,6 +1,7 @@
 TREE_DIRS     = bin lib src \
 		src/driver \
 		src/internal \
+		src/io \
 		src/logic \
 		src/meta \
 		src/output \
diff --git a/src/io/tpax_create_memory_snapshot.c b/src/io/tpax_create_memory_snapshot.c
new file mode 100644
index 0000000..7c3dd7e
--- /dev/null
+++ b/src/io/tpax_create_memory_snapshot.c
@@ -0,0 +1,98 @@
+/**************************************************************/
+/*  tpax: a topological pax implementation                    */
+/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
+/*  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_io_create_memory_snapshot(
+	const struct tpax_driver_ctx *  dctx,
+	int                             fdat,
+	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 */
+	if ((fd = openat(fdat,path,O_CLOEXEC|O_NOCTTY|O_NOFOLLOW,0)) < 0)
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	/* stat compare */
+	if ((fstat(fd,&dstst)) < 0) {
+		close(fd);
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	} else if (tpax_util_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_util_stat_compare(srcst,&dstst)) {
+		close(fd);
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
+	}
+
+	/* yay */
+	close(fd);
+
+	return 0;
+}
diff --git a/src/io/tpax_create_tmpfs_snapshot.c b/src/io/tpax_create_tmpfs_snapshot.c
new file mode 100644
index 0000000..9891e98
--- /dev/null
+++ b/src/io/tpax_create_tmpfs_snapshot.c
@@ -0,0 +1,127 @@
+/**************************************************************/
+/*  tpax: a topological pax implementation                    */
+/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
+/*  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_io_create_tmpfs_snapshot(
+	const struct tpax_driver_ctx *  dctx,
+	int                             fdat,
+	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;
+
+	/* record errors */
+	tpax_driver_set_ectx(
+		dctx,0,path);
+
+	/* tmpfile */
+	if ((fdtmp = tpax_tmpfile()) < 0)
+		return TPAX_SYSTEM_ERROR(dctx);
+
+	/* buffer */
+	buf = tpax_get_driver_anon_map_addr(
+		dctx,&buflen);
+
+	/* open */
+	if ((fdsrc = openat(fdat,path,O_CLOEXEC|O_NOCTTY|O_NOFOLLOW,0)) < 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_util_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_util_stat_compare(srcst,&dstst)) {
+		close(fdsrc);
+		close(fdtmp);
+		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
+	}
+
+	/* yay */
+	close(fdsrc);
+
+	return fdtmp;
+}
diff --git a/src/logic/tpax_archive_write.c b/src/logic/tpax_archive_write.c
index c5109d3..5214787 100644
--- a/src/logic/tpax_archive_write.c
+++ b/src/logic/tpax_archive_write.c
@@ -130,14 +130,14 @@ static int tpax_archive_write_impl(
 
 		/* snapshot */
 		if (membuf) {
-			if (tpax_file_create_memory_snapshot(
+			if (tpax_io_create_memory_snapshot(
 					dctx,fdcwd,path,
 					uctx->st,membuf) < 0)
 				return tpax_archive_write_ret(
 					TPAX_NESTED_ERROR(dctx),
 					uctx);
 		} else {
-			if ((fdtmp = tpax_file_create_tmpfs_snapshot(
+			if ((fdtmp = tpax_io_create_tmpfs_snapshot(
 					dctx,fdcwd,path,
 					uctx->st)) < 0)
 				return tpax_archive_write_ret(
diff --git a/src/logic/tpax_file_create_memory_snapshot.c b/src/logic/tpax_file_create_memory_snapshot.c
deleted file mode 100644
index 504a4a1..0000000
--- a/src/logic/tpax_file_create_memory_snapshot.c
+++ /dev/null
@@ -1,98 +0,0 @@
-/**************************************************************/
-/*  tpax: a topological pax implementation                    */
-/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
-/*  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,
-	int                             fdat,
-	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 */
-	if ((fd = openat(fdat,path,O_CLOEXEC|O_NOCTTY|O_NOFOLLOW,0)) < 0)
-		return TPAX_SYSTEM_ERROR(dctx);
-
-	/* stat compare */
-	if ((fstat(fd,&dstst)) < 0) {
-		close(fd);
-		return TPAX_SYSTEM_ERROR(dctx);
-
-	} else if (tpax_util_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_util_stat_compare(srcst,&dstst)) {
-		close(fd);
-		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
-	}
-
-	/* yay */
-	close(fd);
-
-	return 0;
-}
diff --git a/src/logic/tpax_file_create_tmpfs_snapshot.c b/src/logic/tpax_file_create_tmpfs_snapshot.c
deleted file mode 100644
index 2e92211..0000000
--- a/src/logic/tpax_file_create_tmpfs_snapshot.c
+++ /dev/null
@@ -1,127 +0,0 @@
-/**************************************************************/
-/*  tpax: a topological pax implementation                    */
-/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
-/*  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,
-	int                             fdat,
-	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;
-
-	/* record errors */
-	tpax_driver_set_ectx(
-		dctx,0,path);
-
-	/* tmpfile */
-	if ((fdtmp = tpax_tmpfile()) < 0)
-		return TPAX_SYSTEM_ERROR(dctx);
-
-	/* buffer */
-	buf = tpax_get_driver_anon_map_addr(
-		dctx,&buflen);
-
-	/* open */
-	if ((fdsrc = openat(fdat,path,O_CLOEXEC|O_NOCTTY|O_NOFOLLOW,0)) < 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_util_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_util_stat_compare(srcst,&dstst)) {
-		close(fdsrc);
-		close(fdtmp);
-		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);
-	}
-
-	/* yay */
-	close(fdsrc);
-
-	return fdtmp;
-}