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modstruct: Basic implementation of native struct alignment and types.

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This commit is contained in:
Paul Sokolovsky
2014-04-11 03:47:21 +03:00
parent ef9124f5ff
commit 0c43cf9154
4 changed files with 46 additions and 15 deletions
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47
py/binary.c
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@@ -78,25 +78,54 @@ mp_obj_t mp_binary_get_val_array(char typecode, void *p, int index) {
}
#define is_signed(typecode) (typecode > 'Z')
mp_obj_t mp_binary_get_val_unaligned(char typecode, byte **ptr) {
char type = '<';
mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte **ptr) {
byte *p = *ptr;
uint size = 0, align = 0;
switch (type) {
uint size = 0;
switch (struct_type) {
case '<': case '>':
switch (typecode) {
switch (val_type) {
case 'b': case 'B':
size = 1; break;
case 'h': case 'H':
size = 2; break;
case 'i': case 'I':
size = 4; break;
case 'l': case 'L':
size = 4; break;
}
break;
case '@': {
// TODO:
// The simplest heuristic for alignment is to align by value
// size, but that doesn't work for "bigger than int" types,
// for example, long long may very well have long alignment
// So, we introduce separate alignment handling, but having
// formal support for that is different from actually supporting
// particular (or any) ABI.
uint align = 0;
switch (val_type) {
case 'b': case 'B':
align = size = 1; break;
case 'h': case 'H':
align = size = sizeof(short); break;
case 'i': case 'I':
align = size = sizeof(int); break;
case 'l': case 'L':
align = size = sizeof(long); break;
}
// Make pointer aligned
p = (byte*)(((machine_uint_t)p + align - 1) & ~(align - 1));
#if MP_ENDIANNESS_LITTLE
struct_type = '<';
#else
struct_type = '>';
#endif
break;
}
}
int delta;
if (type == '<') {
if (struct_type == '<') {
delta = -1;
p += size - 1;
} else {
@@ -104,7 +133,7 @@ mp_obj_t mp_binary_get_val_unaligned(char typecode, byte **ptr) {
}
machine_int_t val = 0;
if (is_signed(typecode) && *p & 0x80) {
if (is_signed(val_type) && *p & 0x80) {
val = -1;
}
for (uint i = 0; i < size; i++) {
@@ -113,8 +142,8 @@ mp_obj_t mp_binary_get_val_unaligned(char typecode, byte **ptr) {
p += delta;
}
*ptr += size + align;
if (is_signed(typecode)) {
*ptr += size;
if (is_signed(val_type)) {
return mp_obj_new_int(val);
} else {
return mp_obj_new_int_from_uint(val);