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extmod/vfs_fat_diskio: Use a C-stack-allocated bytearray for block buf. 

This patch eliminates heap allocation in the VFS FAT disk IO layer, when
calling the underlying readblocks/writeblocks methods.  The bytearray
object that is passed to these methods is now allocated on the C stack
rather than the heap (it's only 4 words big).

This means that these methods should not retain a pointer to the buffer
object that is passed in, but this was already a restriction because the
original heap-allocated bytearray had its buffer passed by reference.
This commit is contained in:
Damien George 2018-02-28 15:11:20 +11:00
parent 439acddc60
commit 09be031e04
1 changed files with 6 additions and 2 deletions
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8
extmod/vfs_fat_diskio.c
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@ -36,6 +36,8 @@
#include "py/mphal.h"
#include "py/runtime.h"
#include "py/binary.h"
#include "py/objarray.h"
#include "lib/oofatfs/ff.h"
#include "lib/oofatfs/diskio.h"
#include "extmod/vfs_fat.h"
@ -126,8 +128,9 @@ DRESULT disk_read (
return RES_ERROR;
}
} else {
mp_obj_array_t ar = {{&mp_type_bytearray}, BYTEARRAY_TYPECODE, 0, count * SECSIZE(&vfs->fatfs), buff};
vfs->readblocks[2] = MP_OBJ_NEW_SMALL_INT(sector);
vfs->readblocks[3] = mp_obj_new_bytearray_by_ref(count * SECSIZE(&vfs->fatfs), buff);
vfs->readblocks[3] = MP_OBJ_FROM_PTR(&ar);
mp_call_method_n_kw(2, 0, vfs->readblocks);
// TODO handle error return
}
@ -162,8 +165,9 @@ DRESULT disk_write (
return RES_ERROR;
}
} else {
mp_obj_array_t ar = {{&mp_type_bytearray}, BYTEARRAY_TYPECODE, 0, count * SECSIZE(&vfs->fatfs), (void*)buff};
vfs->writeblocks[2] = MP_OBJ_NEW_SMALL_INT(sector);
vfs->writeblocks[3] = mp_obj_new_bytearray_by_ref(count * SECSIZE(&vfs->fatfs), (void*)buff);
vfs->writeblocks[3] = MP_OBJ_FROM_PTR(&ar);
mp_call_method_n_kw(2, 0, vfs->writeblocks);
// TODO handle error return
}