Function get_buffer_accesses 

pub fn get_buffer_accesses(
    op: u8,
    stack: &[Uint<256, 4>],
) -> Option<BufferAccesses>

A utility function to get the buffer access.

The memory_access variable stores the index on the stack that indicates the buffer offset/len accessed by the given opcode: (read buffer, buffer read offset, buffer read len, write memory offset, write memory len) >= 1: the stack index 0: no memory access -1: a fixed len of 32 bytes -2: a fixed len of 1 byte

The return value is a tuple about accessed buffer region by the given opcode: (read buffer, buffer read offset, buffer read len, write memory offset, write memory len)