Improve readability of MPS reader implementation
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/library/mps_reader.c b/library/mps_reader.c
index a1c0a1c..508f65a 100644
--- a/library/mps_reader.c
+++ b/library/mps_reader.c
@@ -66,6 +66,54 @@
*
*/
+static inline int mps_reader_is_accumulating(
+ mbedtls_mps_reader const *rd )
+{
+ mbedtls_mps_size_t ar;
+ if( rd->acc == NULL )
+ return( 0 );
+
+ ar = rd->acc_share.acc_remaining;
+ return( ar > 0 );
+}
+
+static inline int mps_reader_is_producing(
+ mbedtls_mps_reader const *rd )
+{
+ unsigned char *frag = rd->frag;
+ return( frag == NULL );
+}
+
+static inline int mps_reader_is_consuming(
+ mbedtls_mps_reader const *rd )
+{
+ return( !mps_reader_is_producing( rd ) );
+}
+
+static inline mbedtls_mps_size_t mps_reader_get_fragment_offset(
+ mbedtls_mps_reader const *rd )
+{
+ unsigned char *acc = rd->acc;
+ mbedtls_mps_size_t fo;
+
+ if( acc == NULL )
+ return( 0 );
+
+ fo = rd->acc_share.frag_offset;
+ return( fo );
+}
+
+static inline mbedtls_mps_size_t mps_reader_serving_from_accumulator(
+ mbedtls_mps_reader const *rd )
+{
+ mbedtls_mps_size_t fo, end;
+
+ fo = mps_reader_get_fragment_offset( rd );
+ end = rd->end;
+
+ return( end < fo );
+}
+
static inline void mps_reader_zero( mbedtls_mps_reader *rd )
{
/* A plain memset() would likely be more efficient,
@@ -92,7 +140,9 @@
unsigned char *acc,
mbedtls_mps_size_t acc_len )
{
- MBEDTLS_MPS_TRACE_INIT( "reader_init, acc len %u", (unsigned) acc_len );
+ MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_init" );
+ MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
+ "* Accumulator size: %u bytes", (unsigned) acc_len );
mps_reader_zero( rd );
rd->acc = acc;
rd->acc_len = acc_len;
@@ -101,7 +151,7 @@
int mbedtls_mps_reader_free( mbedtls_mps_reader *rd )
{
- MBEDTLS_MPS_TRACE_INIT( "reader_free" );
+ MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_free" );
mps_reader_zero( rd );
MBEDTLS_MPS_TRACE_RETURN( 0 );
}
@@ -110,31 +160,31 @@
unsigned char *new_frag,
mbedtls_mps_size_t new_frag_len )
{
- unsigned char *acc;
mbedtls_mps_size_t copy_to_acc;
- MBEDTLS_MPS_TRACE_INIT( "reader_feed, frag %p, len %u",
- (void*) new_frag, (unsigned) new_frag_len );
+ MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_feed" );
+ MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
+ "* Fragment length: %u bytes", (unsigned) new_frag_len );
if( new_frag == NULL )
MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_INVALID_ARG );
- MBEDTLS_MPS_STATE_VALIDATE_RAW( rd->frag == NULL,
+ MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_producing( rd ),
"mbedtls_mps_reader_feed() requires reader to be in producing mode" );
- acc = rd->acc;
- if( acc != NULL )
+ if( mps_reader_is_accumulating( rd ) )
{
- mbedtls_mps_size_t aa, ar;
+ unsigned char *acc = rd->acc;
+ mbedtls_mps_size_t ar = rd->acc_share.acc_remaining;
+ mbedtls_mps_size_t aa = rd->acc_avail;
- ar = rd->acc_share.acc_remaining;
- aa = rd->acc_avail;
+ /* Skip over parts of the accumulator that have already been filled. */
+ acc += aa;
copy_to_acc = ar;
if( copy_to_acc > new_frag_len )
copy_to_acc = new_frag_len;
- acc += aa;
-
+ /* Copy new contents to accumulator. */
if( copy_to_acc > 0 )
memcpy( acc, new_frag, copy_to_acc );
@@ -146,21 +196,24 @@
ar -= copy_to_acc;
if( ar > 0 )
{
- /* Need more data */
+ /* We need to accumulate more data. Stay in producing mode. */
aa += copy_to_acc;
rd->acc_share.acc_remaining = ar;
rd->acc_avail = aa;
MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_NEED_MORE );
}
+ /* We have filled the accumulator: Move to consuming mode. */
+
MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
"Enough data available to serve user request" );
+ /* Remember overlap of accumulator and fragment. */
rd->acc_share.frag_offset = aa;
aa += copy_to_acc;
rd->acc_avail = aa;
}
- else
+ else /* Not accumulating */
{
rd->acc_share.frag_offset = 0;
}
@@ -178,33 +231,23 @@
unsigned char **buffer,
mbedtls_mps_size_t *buflen )
{
- unsigned char *frag, *acc;
- mbedtls_mps_size_t end, fo, fl, frag_fetched, frag_remaining;
- MBEDTLS_MPS_TRACE_INIT( "reader_get %p, desired %u",
- (void*) rd, (unsigned) desired );
+ unsigned char *frag;
+ mbedtls_mps_size_t fl, fo, end, frag_fetched, frag_remaining;
+ MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_get" );
+ MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
+ "* Bytes requested: %u", (unsigned) desired );
- frag = rd->frag;
- MBEDTLS_MPS_STATE_VALIDATE_RAW( frag != NULL,
+ MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ),
"mbedtls_mps_reader_get() requires reader to be in consuming mode" );
- /* The fragment offset indicates the offset of the fragment
- * from the accmulator, if the latter is present. Use a offset
- * of \c 0 if no accumulator is used. */
- acc = rd->acc;
- if( acc == NULL )
- fo = 0;
- else
- fo = rd->acc_share.frag_offset;
-
- MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
- "frag_off %u, end %u, acc_avail %d",
- (unsigned) fo, (unsigned) rd->end,
- acc == NULL ? -1 : (int) rd->acc_avail );
+ end = rd->end;
+ fo = mps_reader_get_fragment_offset( rd );
/* Check if we're still serving from the accumulator. */
- end = rd->end;
- if( end < fo )
+ if( mps_reader_serving_from_accumulator( rd ) )
{
+ unsigned char *acc;
+
MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
"Serve the request from the accumulator" );
if( fo - end < desired )
@@ -291,7 +334,9 @@
}
}
+ acc = rd->acc;
acc += end;
+
*buffer = acc;
if( buflen != NULL )
*buflen = desired;
@@ -310,7 +355,6 @@
fl = rd->frag_len;
frag_fetched = end - fo; /* The amount of data from the current fragment
* that has already been passed to the user. */
- frag += frag_fetched;
frag_remaining = fl - frag_fetched; /* Remaining data in fragment */
/* Check if we can serve the read request from the fragment. */
@@ -338,6 +382,10 @@
/* There's enough data in the current fragment to serve the
* (potentially modified) read request. */
+
+ frag = rd->frag;
+ frag += frag_fetched;
+
*buffer = frag;
if( buflen != NULL )
*buflen = desired;
@@ -351,8 +399,8 @@
int mbedtls_mps_reader_commit( mbedtls_mps_reader *rd )
{
mbedtls_mps_size_t end;
- MBEDTLS_MPS_TRACE_INIT( "reader_commit" );
- MBEDTLS_MPS_STATE_VALIDATE_RAW( rd->frag != NULL,
+ MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_commit" );
+ MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ),
"mbedtls_mps_reader_commit() requires reader to be in consuming mode" );
end = rd->end;
@@ -372,19 +420,16 @@
if( paused != NULL )
*paused = 0;
- frag = rd->frag;
- MBEDTLS_MPS_STATE_VALIDATE_RAW( frag != NULL,
+ MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ),
"mbedtls_mps_reader_reclaim() requires reader to be in consuming mode" );
+ frag = rd->frag;
acc = rd->acc;
pending = rd->pending;
commit = rd->commit;
fl = rd->frag_len;
- if( acc == NULL )
- fo = 0;
- else
- fo = rd->acc_share.frag_offset;
+ fo = mps_reader_get_fragment_offset( rd );
if( pending == 0 )
{