142 lines
2.4 KiB
C++
142 lines
2.4 KiB
C++
#include <cstring>
|
|
#include "TLV.h"
|
|
|
|
|
|
#define REC_SIZE(x) ((std::size_t)x.Len + 2)
|
|
|
|
|
|
namespace TLV {
|
|
|
|
|
|
static bool
|
|
space_available(Arena &arena, uint8_t *cursor, uint8_t len)
|
|
{
|
|
uintptr_t remaining = 0;
|
|
|
|
if (cursor == NULL) {
|
|
return false;
|
|
}
|
|
|
|
remaining = (uintptr_t)cursor - (uintptr_t)arena.store;
|
|
remaining = arena.size - remaining;
|
|
return ((size_t)remaining >= ((size_t)len+2));
|
|
}
|
|
|
|
|
|
uint8_t *
|
|
write_to_memory(Arena &arena, uint8_t *cursor, Record &rec)
|
|
{
|
|
// If cursor is NULL, the user needs us to select an empty
|
|
// slot for the record. If we can't find one, that's an
|
|
// error.
|
|
//
|
|
// If, however, the user gives us a cursor, we'll trust it
|
|
// (though space_available will sanity check that cursor).
|
|
if (cursor == NULL) {
|
|
cursor = find_empty(arena, cursor);
|
|
if (cursor == NULL) {
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
if (!space_available(arena, cursor, rec.Len)) {
|
|
return NULL;
|
|
}
|
|
|
|
memcpy(cursor, &rec, REC_SIZE(rec));
|
|
cursor = skip_record(rec, cursor);
|
|
|
|
return cursor;
|
|
}
|
|
|
|
|
|
void
|
|
set_record(Record &rec, uint8_t tag, uint8_t len, const char *val)
|
|
{
|
|
rec.Tag = tag;
|
|
rec.Len = len;
|
|
memcpy(rec.Val, val, len);
|
|
}
|
|
|
|
|
|
void
|
|
read_from_memory(Record &rec, uint8_t *cursor)
|
|
{
|
|
rec.Tag = cursor[0];
|
|
rec.Len = cursor[1];
|
|
memcpy(rec.Val, cursor+2, rec.Len);
|
|
}
|
|
|
|
|
|
/*
|
|
* returns a pointer to memory where the record was found,
|
|
* e.g. find_tag(...)[0] is the tag of the found record.
|
|
*/
|
|
uint8_t *
|
|
find_tag(Arena &arena, uint8_t *cursor, Record &rec)
|
|
{
|
|
uint8_t tag, len;
|
|
|
|
if (cursor == NULL) {
|
|
cursor = arena.store;
|
|
}
|
|
|
|
while ((tag = cursor[0]) != rec.Tag) {
|
|
len = cursor[1];
|
|
if (!space_available(arena, cursor, len)) {
|
|
return NULL;
|
|
}
|
|
cursor += len;
|
|
cursor += 2;
|
|
}
|
|
|
|
if (tag != rec.Tag) {
|
|
return NULL;
|
|
}
|
|
|
|
if (tag != TAG_EMPTY) {
|
|
read_from_memory(rec, cursor);
|
|
cursor = skip_record(rec, cursor);
|
|
}
|
|
return cursor;
|
|
}
|
|
|
|
|
|
uint8_t *
|
|
find_empty(Arena &arena, uint8_t *cursor) {
|
|
Record rec;
|
|
|
|
rec.Tag = TAG_EMPTY;
|
|
return find_tag(arena, cursor, rec);
|
|
}
|
|
|
|
|
|
|
|
uint8_t *
|
|
skip_record(Record &rec, uint8_t *cursor)
|
|
{
|
|
return (uint8_t *)((uintptr_t)cursor + rec.Len + 2);
|
|
}
|
|
|
|
|
|
void
|
|
delete_record(Arena &arena, uint8_t *cursor)
|
|
{
|
|
//
|
|
if (cursor == NULL) {
|
|
return;
|
|
}
|
|
|
|
uintptr_t len = cursor[1] + 2;
|
|
uintptr_t stop = (uintptr_t)arena.size - (uintptr_t)cursor;
|
|
|
|
stop -= len;
|
|
|
|
for (uintptr_t i = (uintptr_t)cursor; i < stop; i++) {
|
|
cursor[i] = cursor[i+len];
|
|
};
|
|
}
|
|
|
|
|
|
} // namespace TLV
|