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40 lines
1015 B
40 lines
1015 B
#include "memory.h"
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#include "../drivers/vga.h"
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// https://wiki.osdev.org/Page_Frame_Allocation
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// page = block
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// MAX_BLOCK_SIZE_IN_BITS/8 bytes
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// i.e. : bit i of byte n define status of block 8n+i
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// block = 8n+i
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// in 32-bit mode, we have access to 2^32 blocks
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// which is (2^32)*BLOCK_SIZE blocks
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// and with a blocksize of 1024, we git around 4.3 trillion blocks
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// which is more than enough
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int bitmap = 0;
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#define CHECK_BITMAP(map, idx) ((map) & (1<<(idx)))
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void mod_bitmap(uint bit, uint bflag) {
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// create a bitmask that will be applied to the bitmap
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int bitmask = 1 << bit;
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// apply the bitmask, resulting in the bit:n bit will bet
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// set to bflag
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bitmap = (((bitmap & ~bitmask)) | (bflag << bit));
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}
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int block_alloc(uint blockidx) {
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if( CHECK_BITMAP(bitmap, blockidx) == 1 ) { // check if block is free
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println("Alloc!", DEFAULT_COLOR);
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mod_bitmap(blockidx, 0);
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return 0; // placeholder
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} else {
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println("ERROR! Attemped to allocate non-free block.", 0x0c);
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return -1;
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}
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}
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