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Force big endian when pushing words

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This ensures that if one wanted to pop a word byte by byte, they'd go
from least to most significance.  Machine independent so that's nice.
This commit is contained in:
Aryadev Chavali
2023-10-15 05:17:33 +01:00
parent 54b836ba64
commit 724f5e0258
1 changed files with 14 additions and 4 deletions
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18
src/main.c
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@@ -60,8 +60,14 @@ void vm_push_word(vm_t *vm, data_t w)
if (vm->stack.pointer + WORD_SIZE >= VM_STACK_MAX) if (vm->stack.pointer + WORD_SIZE >= VM_STACK_MAX)
// TODO: Error STACK_OVERFLOW // TODO: Error STACK_OVERFLOW
return; return;
memcpy(vm->stack.data + vm->stack.pointer, &w.as_word, WORD_SIZE); // By default store in big endian
vm->stack.pointer += WORD_SIZE; for (size_t i = 64; i > 0; i -= 8)
{
const word mask = ((word)0b11111111) << (i - 8);
byte b = (w.as_word & mask) >> (i - 8);
printf("PUSH(%lu): pushed byte %X\n", i, b);
vm_push_byte(vm, DBYTE(b));
}
} }
byte vm_pop_byte(vm_t *vm) byte vm_pop_byte(vm_t *vm)
@@ -78,8 +84,12 @@ word vm_pop_word(vm_t *vm)
// TODO: Error STACK_UNDERFLOW // TODO: Error STACK_UNDERFLOW
return 0; return 0;
word w = 0; word w = 0;
memcpy(&w, vm->stack.data + vm->stack.pointer - WORD_SIZE, WORD_SIZE); for (size_t i = 0; i < WORD_SIZE; ++i)
vm->stack.pointer -= WORD_SIZE; {
byte b = vm_pop_byte(vm);
printf("POP(%lu): popped byte %X\n", i, b);
w = w | ((word)b << (i * 8));
}
return w; return w;
} }