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py/reader: Provide mp_reader_try_read_rom() function.

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This allows accessing data directly in ROM if the reader supports it.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George
2022-03-04 10:54:05 +11:00
parent a1c32101ac
commit f870e8d2d4
2 changed files with 23 additions and 1 deletions
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15
py/reader.c
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@@ -50,7 +50,7 @@ static mp_uint_t mp_reader_mem_readbyte(void *data) {
static void mp_reader_mem_close(void *data) {
mp_reader_mem_t *reader = (mp_reader_mem_t *)data;
if (reader->free_len > 0) {
if (reader->free_len > 0 && reader->free_len != MP_READER_IS_ROM) {
m_del(char, (char *)reader->beg, reader->free_len);
}
m_del_obj(mp_reader_mem_t, reader);
@@ -67,6 +67,19 @@ void mp_reader_new_mem(mp_reader_t *reader, const byte *buf, size_t len, size_t
reader->close = mp_reader_mem_close;
}
const uint8_t *mp_reader_try_read_rom(mp_reader_t *reader, size_t len) {
if (reader->readbyte != mp_reader_mem_readbyte) {
return NULL;
}
mp_reader_mem_t *m = reader->data;
if (m->free_len != MP_READER_IS_ROM) {
return NULL;
}
const uint8_t *data = m->cur;
m->cur += len;
return data;
}
#if MICROPY_READER_POSIX
#include <sys/stat.h>

9
py/reader.h
View File

@@ -28,6 +28,10 @@
#include "py/obj.h"
// Pass to the `free_len` argument to `mp_reader_new_mem` to indicate that the data is in ROM.
// This means that the data is addressable and will remain valid at least until a soft reset.
#define MP_READER_IS_ROM ((size_t)-1)
// the readbyte function must return the next byte in the input stream
// it must return MP_READER_EOF if end of stream
// it can be called again after returning MP_READER_EOF, and in that case must return MP_READER_EOF
@@ -43,4 +47,9 @@ void mp_reader_new_mem(mp_reader_t *reader, const byte *buf, size_t len, size_t
void mp_reader_new_file(mp_reader_t *reader, qstr filename);
void mp_reader_new_file_from_fd(mp_reader_t *reader, int fd, bool close_fd);
// Try to efficiently read the given number of bytes from a ROM-based reader.
// Returns a valid, non-NULL pointer to the requseted data if the reader points to ROM.
// Returns NULL if the reader does not point to ROM.
const uint8_t *mp_reader_try_read_rom(mp_reader_t *reader, size_t len);
#endif // MICROPY_INCLUDED_PY_READER_H