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Improve readability of MPS reader implementation

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Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This commit is contained in:
Hanno Becker 2021-02-08 08:04:01 +00:00
parent 0bea62f2d7
commit f81e41f1e4
1 changed files with 90 additions and 45 deletions
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135
library/mps_reader.c
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@ -66,6 +66,54 @@ static int mbedtls_mps_trace_id = MBEDTLS_MPS_TRACE_BIT_READER;
*
*/
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 @@ int mbedtls_mps_reader_init( mbedtls_mps_reader *rd,
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_init( mbedtls_mps_reader *rd,
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 @@ int mbedtls_mps_reader_feed( mbedtls_mps_reader *rd,
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 @@ int mbedtls_mps_reader_feed( mbedtls_mps_reader *rd,
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 @@ int mbedtls_mps_reader_get( mbedtls_mps_reader *rd,
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 @@ int mbedtls_mps_reader_get( mbedtls_mps_reader *rd,
}
}
acc = rd->acc;
acc += end;
*buffer = acc;
if( buflen != NULL )
*buflen = desired;
@ -310,7 +355,6 @@ int mbedtls_mps_reader_get( mbedtls_mps_reader *rd,
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 @@ int mbedtls_mps_reader_get( mbedtls_mps_reader *rd,
/* 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_get( mbedtls_mps_reader *rd,
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 @@ int mbedtls_mps_reader_reclaim( mbedtls_mps_reader *rd,
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 )
{