diff --git a/include/libcasio/stream.h b/include/libcasio/stream.h
index ec2cd4e..77feebb 100644
--- a/include/libcasio/stream.h
+++ b/include/libcasio/stream.h
@@ -100,8 +100,8 @@ typedef int casio_stream_setattrs_t
 typedef int casio_stream_settm_t
 	OF((void *, const casio_timeouts_t *));
 
-typedef int casio_stream_read_t
-	OF((void *, unsigned char *, size_t *));
+typedef size_t casio_stream_read_t
+	OF((void *, unsigned char *, size_t));
 typedef int casio_stream_write_t
 	OF((void *, const unsigned char *, size_t));
 typedef int casio_stream_seek_t
@@ -359,9 +359,9 @@ CASIO_EXTERN int   CASIO_EXPORT casio_get_lasterr
 
 /* Read and write data from and to a stream. */
 
-CASIO_EXTERN int CASIO_EXPORT casio_read
+CASIO_EXTERN size_t CASIO_EXPORT casio_read
 	OF((casio_stream_t *casio__stream,
-		void *casio__dest, size_t *casio__psize));
+		void *casio__dest, size_t casio__size));
 CASIO_EXTERN int CASIO_EXPORT casio_write
 	OF((casio_stream_t *casio__stream,
 		const void *casio__data, size_t casio__size));
diff --git a/lib/file/file.h b/lib/file/file.h
index 5cd24fc..ec14301 100644
--- a/lib/file/file.h
+++ b/lib/file/file.h
@@ -28,16 +28,15 @@
 /* Read from a stream. */
 
 # define  READ(CASIO__TO, CASIO__SZ) /* normal read */ { \
-	size_t size = CASIO__SZ; \
-	int READ_err = casio_read(buffer, (CASIO__TO), &size); \
-	if (READ_err) return (READ_err); }
-# define FREAD(CASIO__TO, CASIO__SZ) /* fail-less read */ \
-	size_t size = CASIO__SZ; \
-	err = casio_read(buffer, (CASIO__TO), &size);
-# define GREAD(CASIO__TO, CASIO__SZ) /* read with goto fail */ \
-	size_t size = CASIO__SZ; \
-	if ((err = casio_read(buffer, (CASIO__TO), &size))) \
-		goto fail;
+	int READ_err = casio_read(buffer, (CASIO__TO), (CASIO__SZ)); \
+	if (READ_err == -1) return (errno); }
+# define FREAD(CASIO__TO, CASIO__SZ) /* fail-less read */ { \
+	casio_read(buffer, (CASIO__TO), (CASIO__SZ)); \
+	err = errno; }
+# define GREAD(CASIO__TO, CASIO__SZ) /* read with goto fail */ { \
+	casio_read(buffer, (CASIO__TO), (CASIO__SZ)); \
+	if ((err = errno)) \
+		goto fail; }
 
 /* Read using size of the object. */
 
diff --git a/lib/internals.h b/lib/internals.h
index 2823301..de00678 100644
--- a/lib/internals.h
+++ b/lib/internals.h
@@ -26,6 +26,7 @@
 # include <stdlib.h>
 # include <string.h>
 # include <ctype.h>
+# include <errno.h>
 # include "utils/endian.h"
 # include "log/log.h"
 
diff --git a/lib/link/seven/dataflow.c b/lib/link/seven/dataflow.c
index 1c31da1..ab158df 100644
--- a/lib/link/seven/dataflow.c
+++ b/lib/link/seven/dataflow.c
@@ -64,8 +64,10 @@ int CASIO_EXPORT casio_seven_send_buffer(casio_link_t *handle,
 
 		/* Read the big block. */
 		toread = min(BUFSIZE, size);
-		err = casio_read(buffer, buf + 8, &toread);
-		if (err) return (casio_error_noread);
+		toread = casio_read(buffer, buf + 8, toread);
+		if (toread == (size_t)-1) {
+			return (casio_error_noread);
+		}
 		size -= toread;
 
 		/* Send each block. */
@@ -95,7 +97,7 @@ int CASIO_EXPORT casio_seven_send_buffer(casio_link_t *handle,
 	/* Unshift. */
 	if (handle->casio_link_flags & casio_linkflag_shifted)
 		err = casio_seven_unshift(handle);
-
+	return (0);
 fail:
 	return (err);
 }
diff --git a/lib/link/seven/datastream.c b/lib/link/seven/datastream.c
index 456baff..ea8ef2c 100644
--- a/lib/link/seven/datastream.c
+++ b/lib/link/seven/datastream.c
@@ -32,7 +32,6 @@ typedef struct {
 	casio_link_progress_t *_disp;
 	void *_disp_cookie;
 	unsigned int _id, _total;
-	unsigned int _totalsize; /*  */
 	unsigned int _lastsize; /* last packet size */
 
 	/* buffer management */
@@ -52,15 +51,16 @@ typedef struct {
  *	@arg	cookie		the cookie.
  *	@arg	data		the data to read.
  *	@arg	size		the size of the data to read.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-CASIO_LOCAL int casio_seven_data_read(seven_data_cookie_t *cookie,
-	unsigned char *data, size_t *psize)
+CASIO_LOCAL size_t casio_seven_data_read(seven_data_cookie_t *cookie,
+	unsigned char *data, size_t size)
 {
-	int err; size_t tocopy; size_t size = *psize;
+	int err; size_t tocopy;
 	casio_link_t *handle = cookie->_link;
 	unsigned int lastsize = 0;
+	size_t copiedsize = 0;
 
 	/* Check if the stream is faulty. */
 	if (cookie->_faulty)
@@ -72,14 +72,16 @@ CASIO_LOCAL int casio_seven_data_read(seven_data_cookie_t *cookie,
 	if (tocopy) {
 		memcpy(data, &cookie->_current[cookie->_pos], tocopy);
 		cookie->_pos += tocopy;
-		data += tocopy; size -= tocopy;
+		data += tocopy; size -= tocopy; copiedsize += tocopy;
 
-		if (!size) return (0);
+		if (size == 0) return (size);
 	}
 
 	/* Check if we have already finished. */
-	if (cookie->_total && cookie->_id == cookie->_total)
-		return (casio_error_ieof);
+	if (cookie->_total && cookie->_id == cookie->_total) {
+		errno = casio_error_eof;
+		return (-1);
+	}
 
 	/* Receive packets. */
 	while (size) {
@@ -88,8 +90,7 @@ CASIO_LOCAL int casio_seven_data_read(seven_data_cookie_t *cookie,
 		if (err) goto fail;
 		/* If swap roles there is the end of file */
 		if (response.casio_seven_packet_type == casio_seven_type_swp) {
-			*psize = lastsize;
-			return (casio_error_ieof);
+			return copiedsize;
 		}
 		if (response.casio_seven_packet_type != casio_seven_type_data) {
 			msg((ll_error, "Packet wasn't a data packet, wtf?"));
@@ -117,9 +118,10 @@ CASIO_LOCAL int casio_seven_data_read(seven_data_cookie_t *cookie,
 
 		/* Increment and copy. */
 		lastsize = response.casio_seven_packet_data_size;
+		copiedsize += lastsize;
 		if (size >= lastsize) {
 			memcpy(data, response.casio_seven_packet_data, lastsize);
-			data += lastsize; size -= lastsize; cookie->_totalsize += lastsize;
+			data += lastsize; size -= lastsize;
 			continue;
 		}
 
@@ -128,15 +130,15 @@ CASIO_LOCAL int casio_seven_data_read(seven_data_cookie_t *cookie,
 		memcpy(data, response.casio_seven_packet_data, size);
 		memcpy(&cookie->_current[size],
 			&response.casio_seven_packet_data[size], lastsize - size);
-		cookie->_totalsize += lastsize;
-		return (0);
+		return copiedsize;
 	}
 
-	return (0);
+	return copiedsize;
 fail:
 	/* XXX: tell the distant device we have a problem? */
 	cookie->_faulty = 1;
-	return (err);
+	errno = err;
+	return (-1);
 }
 
 /**
@@ -348,7 +350,6 @@ int CASIO_EXPORT casio_seven_open_data_stream(casio_stream_t **stream,
 		cookie->_id = 1;
 		cookie->_total = (unsigned int)(size / BUFSIZE) + !!cookie->_lastsize;
 		cookie->_lastsize = (unsigned int)(size % BUFSIZE);
-		cookie->_totalsize = size;
 		if (!cookie->_lastsize) cookie->_lastsize = BUFSIZE;
 	} else {
 		msg((ll_info, "The data stream is a read one."));
@@ -358,7 +359,6 @@ int CASIO_EXPORT casio_seven_open_data_stream(casio_stream_t **stream,
 		cookie->_id = 0;
 		cookie->_total = 0;
 		cookie->_lastsize = 0;
-		cookie->_totalsize = size;
 	}
 
 	/* initialize the stream */
diff --git a/lib/link/seven/receive.c b/lib/link/seven/receive.c
index ce0a111..43754ad 100644
--- a/lib/link/seven/receive.c
+++ b/lib/link/seven/receive.c
@@ -175,10 +175,9 @@ CASIO_LOCAL const char *gettermstring(casio_seven_term_t code)
 
 #define buffer handle->casio_link_recv_buffer
 #define COMPLETE_PACKET(N) { \
-	size_t size##__LINE__ = (size_t)N; \
 	int COMP_PACKET_err = casio_read(handle->casio_link_stream, \
-		&buffer[received], &size##__LINE__); \
-	received += size##__LINE__; if (COMP_PACKET_err) return (COMP_PACKET_err); }
+		&buffer[received], (size_t)N); \
+	received += COMP_PACKET_err; if (COMP_PACKET_err == -1) return (errno); }
 
 CASIO_LOCAL int casio_seven_decode(casio_link_t *handle, int scralign)
 {
diff --git a/lib/link/seven/scsi.c b/lib/link/seven/scsi.c
index cc79567..86ea65a 100644
--- a/lib/link/seven/scsi.c
+++ b/lib/link/seven/scsi.c
@@ -83,24 +83,27 @@ typedef struct {
  * Read and write from the stream.
  * --- */
 
-CASIO_LOCAL int seven_scsi_read(seven_scsi_cookie_t *cookie,
-	unsigned char *buffer, size_t *size)
+CASIO_LOCAL size_t seven_scsi_read(seven_scsi_cookie_t *cookie,
+	unsigned char *buffer, size_t size)
 {
 	casio_scsi_t scsi; int err;
+	size_t copiedsize = 0;
 
 	/* Empty what's already in the buffer. */
 
 	if (cookie->left) {
-		if (cookie->left >= *size) {
-			memcpy(buffer, cookie->ptr, *size);
-			cookie->ptr += *size;
-			cookie->left -= *size;
-			return (0);
+		if (cookie->left >= size) {
+			memcpy(buffer, cookie->ptr, size);
+			cookie->ptr += size;
+			cookie->left -= size;
+			copiedsize += cookie->left;
+			return copiedsize;
 		}
 
 		memcpy(buffer, cookie->ptr, cookie->left);
 		buffer += cookie->left;
-		*size -= cookie->left;
+		size -= cookie->left;
+		copiedsize += cookie->left;
 		reset_cookie(cookie);
 	}
 
@@ -125,8 +128,10 @@ CASIO_LOCAL int seven_scsi_read(seven_scsi_cookie_t *cookie,
 			scsi.casio_scsi_data = poll_data;
 			scsi.casio_scsi_data_len = 16;
 
-			if ((err = casio_scsi_request(cookie->stream, &scsi)))
-				return (err);
+			if ((err = casio_scsi_request(cookie->stream, &scsi))) {
+				errno = err;
+				return (-1);
+			}
 
 			mem((ll_info, poll_data, 16));
 
@@ -151,14 +156,14 @@ CASIO_LOCAL int seven_scsi_read(seven_scsi_cookie_t *cookie,
 		 * We could also check that `avail < 0x10000` because we need to
 		 * express it later, but it is imposed by the source format. */
 
-		if (avail > *size && *size <= cookie->size) {
+		if (avail > size && size <= cookie->size) {
 			to = cookie->ptr;
 			if (avail > cookie->size)
 				avail = cookie->size;
 		} else {
 			to = buffer;
-			if (avail > *size)
-				avail = *size;
+			if (avail > size)
+				avail = size;
 		}
 
 		/* Actually get the data. */
@@ -176,24 +181,27 @@ CASIO_LOCAL int seven_scsi_read(seven_scsi_cookie_t *cookie,
 			scsi.casio_scsi_data = cookie->ptr;
 			scsi.casio_scsi_data_len = avail;
 
-			if ((err = casio_scsi_request(cookie->stream, &scsi)))
-				return (err);
+			if ((err = casio_scsi_request(cookie->stream, &scsi))) {
+				errno = err;
+				return (-1);
+			}
 		}
 
 		if (to == buffer) {
 			buffer += avail;
-			*size -= avail;
+			size -= avail;
 		} else {
 			cookie->left = avail;
 
-			memcpy(buffer, cookie->ptr, *size);
-			cookie->ptr += *size;
-			cookie->left -= *size;
-			*size = 0;
+			memcpy(buffer, cookie->ptr, size);
+			cookie->ptr += size;
+			cookie->left -= size;
+			copiedsize += size;
+			size = 0;
 		}
-	} while (*size);
+	} while (size);
 
-	return (0);
+	return copiedsize;
 }
 
 CASIO_LOCAL int seven_scsi_write(seven_scsi_cookie_t *cookie,
diff --git a/lib/mcsfile/mcsfile.h b/lib/mcsfile/mcsfile.h
index ee61550..8d68e99 100644
--- a/lib/mcsfile/mcsfile.h
+++ b/lib/mcsfile/mcsfile.h
@@ -26,20 +26,15 @@
 
 /* Read from a stream. */
 
-/* FIXME : size_t size##__LINE__ = CASIO__SZ;
- * Replace this by other thing that is more futur proof
-*/
-
 # define  READ(CASIO__TO, CASIO__SZ) /* normal read */ { \
-	size_t size##__LINE__ = CASIO__SZ; \
-	int READ_err = casio_read(buffer, (CASIO__TO), &size##__LINE__); \
-	if (READ_err) return (READ_err); }
+	int READ_err = casio_read(buffer, (CASIO__TO), (CASIO__SZ)); \
+	if (READ_err == -1) return (errno); }
 # define FREAD(CASIO__TO, CASIO__SZ) /* fail-less read */ { \
-	size_t size##__LINE__ = CASIO__SZ; \
-	err = casio_read(buffer, (CASIO__TO), &size##__LINE__); }
+	casio_read(buffer, (CASIO__TO), (CASIO__SZ)); \
+	err = errno; }
 # define GREAD(CASIO__TO, CASIO__SZ) /* read with goto fail */ { \
-	size_t size##__LINE__ = CASIO__SZ; \
-	if ((err = casio_read(buffer, (CASIO__TO), &size##__LINE__))) \
+	casio_read(buffer, (CASIO__TO), (CASIO__SZ)); \
+	if ((err = errno)) \
 		goto fail; }
 
 /* Read using size of the object. */
diff --git a/lib/stream/builtin/csum32.c b/lib/stream/builtin/csum32.c
index 3169f28..3e3a439 100644
--- a/lib/stream/builtin/csum32.c
+++ b/lib/stream/builtin/csum32.c
@@ -38,24 +38,26 @@ struct thecookie {
  *	@arg	cookie		the cookie.
  *	@arg	data		the data pointer.
  *	@arg	size		the data size.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-CASIO_LOCAL int csum32_read(struct thecookie *cookie,
-	unsigned char *dest, size_t *psize)
+CASIO_LOCAL size_t csum32_read(struct thecookie *cookie,
+	unsigned char *dest, size_t size)
 {
 	int err;
-	size_t size = *psize;
 
 	/* Make the call. */
 
-	err = casio_read(cookie->_stream, dest, &size);
-	if (err) return (err);
+	size = casio_read(cookie->_stream, dest, size);
+	if (size == (size_t)-1) {
+		errno = errno;
+		return (-1);
+	}
 
 	/* Make the checksum. */
 
 	*cookie->_checksum = casio_checksum32(dest, size, *cookie->_checksum);
-	return (0);
+	return size;
 }
 
 /**
diff --git a/lib/stream/builtin/file.c b/lib/stream/builtin/file.c
index 90fc051..b3deb5d 100644
--- a/lib/stream/builtin/file.c
+++ b/lib/stream/builtin/file.c
@@ -46,14 +46,14 @@ typedef struct {
  *	@arg	cookie		the cookie.
  *	@arg	data		the data pointer
  *	@arg	size		the data size.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-CASIO_LOCAL int casio_file_read(file_cookie_t *cookie,
-	unsigned char *dest, size_t *psize)
+CASIO_LOCAL size_t casio_file_read(file_cookie_t *cookie,
+	unsigned char *dest, size_t size)
 {
 	size_t recv;
-	size_t size = *psize;
+	size_t copiedsize = 0;
 
 	/* Main receiving loop. */
 
@@ -67,6 +67,7 @@ CASIO_LOCAL int casio_file_read(file_cookie_t *cookie,
 
 		dest = (void*)((char*)dest + recv);
 		size -= recv;
+		copiedsize += recv;
 
 		/* Check the error. */
 
@@ -91,7 +92,8 @@ CASIO_LOCAL int casio_file_read(file_cookie_t *cookie,
 			/* End of file. */
 
 			msg((ll_error, "encountered an end of file"));
-			return (casio_error_eof);
+			errno = casio_error_eof;
+			return (-1);
 
 		case EINTR: /* alarm */
 		case ETIMEDOUT:
@@ -101,21 +103,24 @@ CASIO_LOCAL int casio_file_read(file_cookie_t *cookie,
 			/* A timeout has occurred. */
 
 			msg((ll_error, "timeout received"));
-			return (casio_error_timeout);
+			errno = casio_error_timeout;
+			return (-1);
 
 		case ENODEV:
 		case EPIPE: case ESPIPE:
 			/* A device error has occured. */
 
 			msg((ll_error, "calculator was disconnected"));
-			return (casio_error_nocalc);
+			errno = casio_error_nocalc;
+			return (-1);
 
 		default:
 			msg((ll_fatal, "errno was %d: %s", errno, strerror(errno)));
-			return (casio_error_unknown);
+			errno = casio_error_unknown;
+			return (-1);
 	}
 
-	return (0);
+	return copiedsize;
 }
 
 /**
diff --git a/lib/stream/builtin/libusb/libusb.h b/lib/stream/builtin/libusb/libusb.h
index b2dea05..75196b9 100644
--- a/lib/stream/builtin/libusb/libusb.h
+++ b/lib/stream/builtin/libusb/libusb.h
@@ -58,9 +58,9 @@ CASIO_EXTERN int CASIO_EXPORT casio_libusb_settm
 
 /* Character device callbacks. */
 
-CASIO_EXTERN int CASIO_EXPORT casio_libusb_read
+CASIO_EXTERN size_t CASIO_EXPORT casio_libusb_read
 	OF((cookie_libusb_t *casio__cookie,
-		unsigned char *casio__dest, size_t *casio__psize));
+		unsigned char *casio__dest, size_t casio__size));
 CASIO_EXTERN int CASIO_EXPORT casio_libusb_write
 	OF((cookie_libusb_t *casio__cookie,
 		const unsigned char *casio__data, size_t casio__size));
diff --git a/lib/stream/builtin/libusb/read.c b/lib/stream/builtin/libusb/read.c
index e8badeb..9859394 100644
--- a/lib/stream/builtin/libusb/read.c
+++ b/lib/stream/builtin/libusb/read.c
@@ -26,15 +26,15 @@
  *	@arg	vcookie		the cookie (voided)
  *	@arg	data		the data pointer.
  *	@arg	size		the data size.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-int CASIO_EXPORT casio_libusb_read(cookie_libusb_t *cookie,
-	unsigned char *dest, size_t *psize)
+size_t CASIO_EXPORT casio_libusb_read(cookie_libusb_t *cookie,
+	unsigned char *dest, size_t size)
 {
 	int libusberr;
 	size_t tocopy;
-	size_t size = *psize;
+	size_t copiedsize = 0;
 
 	/* Transmit what's already in the buffer. */
 
@@ -46,6 +46,7 @@ int CASIO_EXPORT casio_libusb_read(cookie_libusb_t *cookie,
 		cookie->_start += tocopy;
 		dest += tocopy;
 		size -= tocopy;
+		copiedsize += tocopy;
 	}
 
 	/* Main receiving loop. */
@@ -65,15 +66,18 @@ int CASIO_EXPORT casio_libusb_read(cookie_libusb_t *cookie,
 		case LIBUSB_ERROR_NO_DEVICE:
 		case LIBUSB_ERROR_IO:
 			msg((ll_error, "The calculator is not here anymore :("));
-			return (casio_error_nocalc);
+			errno = casio_error_nocalc;
+			return (-1);
 
 		case LIBUSB_ERROR_TIMEOUT:
-			return (casio_error_timeout);
+			errno = casio_error_timeout;
+			return (-1);
 
 		default:
 			msg((ll_fatal, "libusb error was %d: %s", libusberr,
 				libusb_strerror(libusberr)));
-			return (casio_error_unknown);
+			errno = casio_error_unknown;
+			return (-1);
 		}
 
 		/* Get the current size to copy. */
@@ -88,13 +92,17 @@ int CASIO_EXPORT casio_libusb_read(cookie_libusb_t *cookie,
 		dest += tocopy;
 		size -= tocopy;
 
+		/* Increment the total copied size */
+
+		copiedsize += tocopy;
+
 		/* Correct start and end points. */
 
 		cookie->_start = tocopy;
 		cookie->_end = (size_t)recv - 1;
 	}
 
-	return (0);
+	return copiedsize;
 }
 
 #endif
diff --git a/lib/stream/builtin/limited.c b/lib/stream/builtin/limited.c
index 5b6a244..d07a84d 100644
--- a/lib/stream/builtin/limited.c
+++ b/lib/stream/builtin/limited.c
@@ -37,35 +37,39 @@ typedef struct {
  *	@arg	vcookie		the cookie (uncasted).
  *	@arg	data		the data pointer.
  *	@arg	size		the data size.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-CASIO_LOCAL int casio_limited_read(void *vcookie, unsigned char *dest,
-	size_t *psize)
+CASIO_LOCAL size_t casio_limited_read(void *vcookie, unsigned char *dest,
+	size_t size)
 {
 	int err; limited_cookie_t *cookie = (void*)vcookie;
-	size_t left; size_t size = *psize;
+	size_t left; size_t copiedsize;
 
 	if (size > cookie->_left) {
 		/* First, skip the required bytes. */
 
 		left = cookie->_left;
 		cookie->_left = 0;
-		if ((err = casio_skip(cookie->_stream, left)))
-			return (err);
+		if ((err = casio_skip(cookie->_stream, left))) {
+			errno = err;
+			return (-1);
+		}
 
 		/* Once the skip is done successfully, we return that we
 		 * have an EOF. */
-
-		return (casio_error_eof);
+		errno = casio_error_eof;
+		return (-1);
 	}
 
-	if ((err = casio_read(cookie->_stream, dest, &size))) {
+	size = casio_read(cookie->_stream, dest, size);
+	if (size == (size_t)-1) {
 		cookie->_left = 0; /* XXX: depends on the error? */
-		return (err);
+		errno = errno;
+		return (-1);
 	}
 	cookie->_left -= size;
-	return (0);
+	return size;
 }
 
 /**
diff --git a/lib/stream/builtin/memory.c b/lib/stream/builtin/memory.c
index 0fd8b5a..33fa8e6 100644
--- a/lib/stream/builtin/memory.c
+++ b/lib/stream/builtin/memory.c
@@ -35,25 +35,27 @@ typedef struct {
  *	@arg	vcookie		the cookie (uncasted)
  *	@arg	data		the data pointer.
  *	@arg	size		the data size.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-CASIO_LOCAL int casio_memory_read(void *vcookie, unsigned char *dest, size_t *psize)
+CASIO_LOCAL size_t casio_memory_read(void *vcookie, unsigned char *dest, size_t size)
 {
 	memory_cookie_t *cookie = (void*)vcookie;
-	size_t size = *psize;
 
-	if (((size_t)-1 - cookie->_offset) < size) /* overflow */
-		return (casio_error_read);
+	if (((size_t)-1 - cookie->_offset) < size) { /* overflow */
+		errno = casio_error_read;
+		return (-1);
+	}
 	if (cookie->_offset + (casio_off_t)size > cookie->_size) {
 		cookie->_offset = cookie->_size - 1;
-		return (casio_error_eof);
+		errno = casio_error_eof;
+		return (-1);
 	}
 
 	memcpy(dest, &cookie->_memory[cookie->_offset], size);
 	cookie->_offset += size;
 
-	return (0);
+	return size;
 }
 
 /**
diff --git a/lib/stream/builtin/streams/read.c b/lib/stream/builtin/streams/read.c
index d3cf63a..2f61377 100644
--- a/lib/stream/builtin/streams/read.c
+++ b/lib/stream/builtin/streams/read.c
@@ -26,14 +26,14 @@
  *	@arg	cookie		the cookie.
  *	@arg	data		the data pointer.
  *	@arg	size		the data size.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-int CASIO_EXPORT casio_streams_read(streams_cookie_t *cookie,
-	unsigned char *dest, size_t *psize)
+size_t CASIO_EXPORT casio_streams_read(streams_cookie_t *cookie,
+	unsigned char *dest, size_t size)
 {
 	int fd = cookie->_readfd;
-	size_t size = *psize;
+	size_t copiedsize = 0;
 
 	/* Transmit what's already in the buffer. */
 
@@ -45,6 +45,7 @@ int CASIO_EXPORT casio_streams_read(streams_cookie_t *cookie,
 		cookie->_start += tocopy;
 		dest += tocopy;
 		size -= tocopy;
+		copiedsize += tocopy;
 	}
 
 	/* Main receiving loop. */
@@ -68,7 +69,8 @@ int CASIO_EXPORT casio_streams_read(streams_cookie_t *cookie,
 			default:
 				msg((ll_fatal, "error was %d: %s",
 					errno, strerror(errno)));
-				return (casio_error_unknown);
+				errno = casio_error_unknown;
+				return (-1);
 		}
 
 		/* Get the current size to copy. */
@@ -82,13 +84,17 @@ int CASIO_EXPORT casio_streams_read(streams_cookie_t *cookie,
 		dest += tocopy;
 		size -= tocopy;
 
+		/* Increment total size copied */
+
+		copiedsize += tocopy;
+
 		/* Correct start and end points. */
 
 		cookie->_start = tocopy;
 		cookie->_end = (size_t)recv - 1;
 	}
 
-	return (0);
+	return copiedsize;
 }
 
 #endif
diff --git a/lib/stream/builtin/streams/streams.h b/lib/stream/builtin/streams/streams.h
index d1e71eb..d884a1c 100644
--- a/lib/stream/builtin/streams/streams.h
+++ b/lib/stream/builtin/streams/streams.h
@@ -51,9 +51,9 @@ CASIO_EXTERN int CASIO_EXPORT casio_streams_settm
 
 /* Character device callbacks. */
 
-CASIO_EXTERN int CASIO_EXPORT casio_streams_read
+CASIO_EXTERN size_t CASIO_EXPORT casio_streams_read
 	OF((streams_cookie_t *casio__cookie,
-		unsigned char *casio__dest, size_t *casio__psize));
+		unsigned char *casio__dest, size_t casio__size));
 CASIO_EXTERN int CASIO_EXPORT casio_streams_write
 	OF((streams_cookie_t *casio__cookie,
 		const unsigned char *casio__data, size_t casio__size));
diff --git a/lib/stream/read.c b/lib/stream/read.c
index 3a70350..9c1028e 100644
--- a/lib/stream/read.c
+++ b/lib/stream/read.c
@@ -25,32 +25,37 @@
  *	@arg	stream		the stream to read from.
  *	@arg	dest		the destination buffer.
  *	@arg	size		the amount of bytes to read.
- *	@return				the error code (0 if ok).
+ *	@return				the size written and -1 if error (error code is in errno).
  */
 
-int CASIO_EXPORT casio_read(casio_stream_t *stream, void *dest, size_t *psize)
+size_t CASIO_EXPORT casio_read(casio_stream_t *stream, void *dest, size_t size)
 {
-	int err;
+	int err = casio_error_ok;
 
 	/* check if we can read */
 	failure(~stream->casio_stream_mode & CASIO_OPENMODE_READ, casio_error_read)
 
 	/* read */
-	if (!(*psize)) return (0);
-	if (!psize) {
-		size_t size = -1;
-		err = (*getcb(stream, read))(stream->casio_stream_cookie, dest, &size);
-	} else {
-		err = (*getcb(stream, read))(stream->casio_stream_cookie, dest, psize);
-	}
-	if (err && err != casio_error_ieof) {
+	if (size == 0) return (0);
+
+	size = (*getcb(stream, read))(stream->casio_stream_cookie, dest, size);
+	
+	if (size == (size_t)-1) {
+		err = errno;
+		if (err == casio_error_eof) {
+			msg((ll_info, "Stream reading get to the end (EOF)"));
+			goto fail;
+		}
 		msg((ll_error, "Stream reading failure: %s", casio_strerror(err)));
 		goto fail;
 	}
 
 	/* move the cursor and return */
-	stream->casio_stream_offset += *psize;
+	if(size != 1) {
+		stream->casio_stream_offset += size;
+	}
 fail:
 	stream->casio_stream_lasterr = err;
-	return (err);
+	errno = err;
+	return size;
 }
diff --git a/lib/stream/seek.c b/lib/stream/seek.c
index 419e53f..c688d0d 100644
--- a/lib/stream/seek.c
+++ b/lib/stream/seek.c
@@ -63,9 +63,11 @@ int CASIO_EXPORT casio_seek(casio_stream_t *stream, casio_off_t offset,
 				size_t rd = min(to_skip, 128);
 
 				/* Read that much from the stream. */
-
-				if ((err = casio_read(stream, buf, &rd)))
+				size_t readed = casio_read(stream, buf, rd);
+				if (readed == (size_t)-1) {
+					err = errno;
 					goto fail;
+				}
 
 				to_skip -= rd;
 			} while (to_skip);
diff --git a/src/p7/main.c b/src/p7/main.c
index b87943c..1794a6b 100644
--- a/src/p7/main.c
+++ b/src/p7/main.c
@@ -316,11 +316,11 @@ int main(int ac, char **av)
 			size_t size;
 			do
 			{
-				size = sizeof(buffer);
-				err = casio_read(fileStream, buffer, &size);
+				size = casio_read(fileStream, buffer, sizeof(buffer));
+				if(size == (size_t)-1)
+					err = errno;
+				if(err == casio_error_eof)
 				fwrite(buffer, 1, size, file);
-				if(err == casio_error_ieof)
-					break;
 			} while (err == 0);
 			
 			/* All good so close streams and clear error */
diff --git a/src/p7/main.h b/src/p7/main.h
index 2242152..f48fe23 100644
--- a/src/p7/main.h
+++ b/src/p7/main.h
@@ -20,6 +20,7 @@
 # define MAIN_H
 # include <stdio.h>
 # include <libcasio.h>
+# include <errno.h>
 
 /* Menus */
 typedef enum {
diff --git a/src/p7os/procs/fxremote_flash.c b/src/p7os/procs/fxremote_flash.c
index 7d53bb0..7fdc13c 100644
--- a/src/p7os/procs/fxremote_flash.c
+++ b/src/p7os/procs/fxremote_flash.c
@@ -60,7 +60,7 @@ struct data_copy_block {
 static int send_sector(casio_link_t *handle, casio_stream_t *buffer,
 	unsigned long addr, unsigned long size)
 {
-	int err, buf_err;
+	int err;
 	osdisp_t osdisp_cookie;
 
 	/* Sending the data to the Update.Exe's. */
@@ -83,7 +83,8 @@ static int send_sector(casio_link_t *handle, casio_stream_t *buffer,
 			/* Prepare the block. */
 			block.destination = casio_be32toh(buf);
 			block.length      = casio_be32toh(len);
-			if ((buf_err = casio_read(buffer, block.data, &len))) {
+			len = casio_read(buffer, block.data, len);
+			if (len == (size_t)-1) {
 				osdisp_interrupt(&osdisp_cookie);
 				return (casio_error_read);
 			}
diff --git a/src/p7os/procs/std_prepare.c b/src/p7os/procs/std_prepare.c
index 6663169..5e13a80 100644
--- a/src/p7os/procs/std_prepare.c
+++ b/src/p7os/procs/std_prepare.c
@@ -55,7 +55,7 @@ int prepare(args_t *args)
 	/* Sleep while the software on the calculator sets up the
 	 * communication interface. */
 	printf("Waiting for the Update.Exe to set up the communication...\n");
-	casio_sleep(1000);
+	casio_sleep(3000);
 
 	err = 0;
 fail: