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#include "memory.h"
void MemoryAccess::write_hword(std::uint32_t offset, std::uint16_t value) {
this->write_byte(offset++, (std::uint8_t)value);
this->write_byte(offset, (std::uint8_t)(value >> 8));
}
void MemoryAccess::write_word(std::uint32_t offset, std::uint32_t value) {
this->write_byte(offset++, (std::uint8_t)value);
this->write_byte(offset++, (std::uint8_t)(value >> 8));
this->write_byte(offset++, (std::uint8_t)(value >> 16));
this->write_byte(offset++, (std::uint8_t)(value >> 24));
}
std::uint16_t MemoryAccess::read_hword(std::uint32_t offset) {
std::uint16_t dt = 0;
dt |= this->read_byte(offset++);
dt |= (this->read_byte(offset) << 8);
return dt;
}
std::uint32_t MemoryAccess::read_word(std::uint32_t offset) {
std::uint32_t dt = 0;
dt |= this->read_byte(offset++);
dt |= (this->read_byte(offset++) << 8);
dt |= (this->read_byte(offset++) << 16);
dt |= (this->read_byte(offset) << 24);
return dt;
}
MemorySection::MemorySection(std::uint32_t length) {
this->length = length;
this->dt = new std::uint8_t[length];
}
MemorySection::~MemorySection() {
delete this->dt;
}
using namespace std;
void MemorySection::write_byte(std::uint32_t offset, std::uint8_t value) {
if (offset >= this->length)
throw QTMIPS_EXCEPTION(OutOfMemoryAccess, "Trying to write outside of the memory section", std::string("Accessing using offset: ") + std::to_string(offset));
this->dt[offset] = value;
}
std::uint8_t MemorySection::read_byte(std::uint32_t offset) {
if (offset >= this->length)
throw QTMIPS_EXCEPTION(OutOfMemoryAccess, "Trying to read outside of the memory section", std::string("Accessing using offset: ") + std::to_string(offset));
return this->dt[offset];
}
// Number of bites per row on lookup tree
#define MEMORY_TREE_ROW ((32 - MEMORY_SECTION_BITS) / MEMORY_TREE_H)
// Size of row in memory lookup tree
#define MEMORY_TREE_LEN (1 << MEMORY_TREE_ROW)
// Just do some sanity checks
#if (MEMORY_TREE_LEN == 0)
#error Nonzero memory tree row size
#endif
#if (((32 - MEMORY_SECTION_BITS) % MEMORY_TREE_H) != 0)
#error Memory tree is not fully divisible by memory tree height
#endif
#if (MEMORY_TREE_H < 2)
#error Memory tree have to be higher or in limit equal to two
#endif
union MemoryTree {
union MemoryTree *mt;
MemorySection *sec;
};
Memory::Memory() {
this->mt_root = allocate_section_tree();
}
Memory::~Memory() {
// Free up memory tree
// TODO
}
union MemoryTree *Memory::allocate_section_tree() {
union MemoryTree *mt = new union MemoryTree[MEMORY_TREE_LEN];
for (size_t i = 0; i < MEMORY_TREE_LEN; i++)
// Note that this also nulls sec pointer as those are both pointers and so they have same size
mt[i].mt = nullptr;
return mt;
}
// Create address mask with section length
#define ADDRESS_MASK(LEN) ((1 << LEN) - 1)
// Get index in tree node from address, length of row and tree depth
// ADDR is expected to be and address with lowest bites removed (MEMORY_SECTION_BITS)
#define ADDRESS_TREE_INDEX(DEPTH, ADDR) ((ADDR >> (DEPTH * MEMORY_TREE_ROW)) & ADDRESS_MASK(MEMORY_TREE_ROW))
MemorySection *Memory::get_section(std::uint32_t address, bool create) {
std::uint32_t addr = address >> MEMORY_SECTION_BITS; // drop all bits for addressing inside of the section
union MemoryTree *w = this->mt_root;
size_t ii;
for (int i = 0; i < (MEMORY_TREE_H - 1); i++) {
ii = ADDRESS_TREE_INDEX(i, addr);
if (w[ii].mt == nullptr) { // We don't have this tree so allocate it
if (!create) // If we shouldn't be creating it than just return null
return nullptr;
w[ii].mt = allocate_section_tree();
}
w = w[ii].mt;
}
// Now expand last level
ii = ADDRESS_TREE_INDEX((MEMORY_TREE_H - 1), addr);
if (w[ii].sec == nullptr) {
if (!create)
return nullptr;
w[ii].sec = new MemorySection(1 << MEMORY_SECTION_BITS);
}
return w[ii].sec;
}
// Note about this address magic: we want to mask upper bits in address as those were used
// for section lookup. We do it using (2^BITS - 1).
#define SECTION_ADDRESS(ADDR) (ADDR & ADDRESS_MASK(MEMORY_SECTION_BITS))
void Memory::write_byte(std::uint32_t address, std::uint8_t value) {
MemorySection *section = this->get_section(address, true);
section->write_byte(SECTION_ADDRESS(address), value);
}
std::uint8_t Memory::read_byte(std::uint32_t address) {
MemorySection *section = this->get_section(address, true);
if (section == nullptr)
return 0;
else
return section->read_byte(SECTION_ADDRESS(address));
}
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