Difference between revisions of "C51 Malloc"

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m (Talcall moved page Calculate Available RAM Address to C51 Malloc: libc)
 
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  no idea what the math is about. Seems to count how many bytes are between 0x0004e9d4 and + input/0x800 or + 0x40, whichever is smaller. also notes highest order non-zero value(?)
+
  uses r4 input to determine the size of the requested file in bytes; finds and returns the address of the first unused sect of data after 0x801df000 in blocks of 0x800.
  if a non-zero number is encountered wrongly, the game very dies, I could imagine it would immediately fry and set alight hardware
+
  r4 values between 0x1 and 0x7ff all dedicate 1 block of space, but a block size request of 0x800 for example would require 2 blocks. this is accounted for.
stores the final r7 result to each byte, which is the largest encountered value + 0x1
 
May load LBA of something not a map if a non-zero value is encountered.
 
grabs something from very close to the beginning of scus
 
if r4 = 0x00020000 & r2 = 0, load map LBA pointer(?)
 
 
   
 
   
 
  00044414: 27bdfff8 addiu r29,r29,0xfff8
 
  00044414: 27bdfff8 addiu r29,r29,0xfff8

Latest revision as of 07:50, 6 July 2023

uses r4 input to determine the size of the requested file in bytes; finds and returns the address of the first unused sect of data after 0x801df000 in blocks of 0x800.
r4 values between 0x1 and 0x7ff all dedicate 1 block of space, but a block size request of 0x800 for example would require 2 blocks. this is accounted for.

00044414: 27bdfff8 addiu r29,r29,0xfff8
00044418: 00002821 addu r5,r0,r0			#r5 = 0
0004441c: 000432c2 srl r6,r4,0x0b			#r6 = input >> 0xb (0x800 to 0x1)
00044420: 308407ff andi r4,r4,0x07ff			#
00044424: 10800002 beq r4,r0,0x00044430		#branch if input && 0x07ff is 0
00044428: 34070001 ori r7,r0,0x0001			#r7 = 1
0004442c: 24c60001 addiu r6,r6,0x0001			#r6 = Ceil(input>>0xb)
00044430: 00002021 addu r4,r0,r0			#r4 = 0
00044434: 3c018005 lui r1,0x8005
00044438: 00240821 addu r1,r1,r4
0004443c: 9023e9d4 lbu r3,-0x162c(r1)			#loads byte from 0x8004e9d4 + r4
00044440: 00000000 nop
00044444: 1460000a bne r3,r0,0x00044470		#branch if not 0
00044448: 0067102b sltu r2,r3,r7			#true if r3 < r7
0004444c: 14a00002 bne r5,r0,0x00044458
00044450: 00000000 nop
00044454: 00804021 addu r8,r4,r0			#r8 = r4 (largest address non-zero value in loop space?)
00044458: 24a50001 addiu r5,r5,0x0001			#r5 + 1
0004445c: 00a6102b sltu r2,r5,r6			#set true if r5 < Ceil(input>>0xb)
00044460: 1040000c beq r2,r0,0x00044494		#branch when looped Ceil(input>>0xb) times
00044464: 00000000 nop					#remembers number of times looped (r5)
00044468: 08011120 j 0x00044480
0004446c: 24840001 addiu r4,r4,0x0001			#r4 + 1
00044470: 14400002 bne r2,r0,0x0004447c		#branch if r3 < r7
00044474: 00002821 addu r5,r0,r0			#r5 = 0
00044478: 24670001 addiu r7,r3,0x0001			#r7 = byte + 1
0004447c: 24840001 addiu r4,r4,0x0001			#r4 + 1
00044480: 2c820040 sltiu r2,r4,0x0040			#set true if r4 < 0x40 (hardcoded safeguard?)
00044484: 1440ffeb bne r2,r0,0x00044434		#loop if still yet to loop 0x40 times
00044488: 00a6102b sltu r2,r5,r6			#set true if r5 < Ceil(input>>0xb)
0004448c: 14400010 bne r2,r0,0x000444d0		#branch if so
00044490: 00001021 addu r2,r0,r0			#r2 = 0
00044494: 10a0000a beq r5,r0,0x000444c0		#branch if looped 0 times
00044498: 00002021 addu r4,r0,r0			#r4 = 0
0004449c: 3c038005 lui r3,0x8005
000444a0: 2463e9d4 addiu r3,r3,-0x162c			#r3 = 0x8004e9d4
000444a4: 01041021 addu r2,r8,r4			#r2 = r8 + r4
000444a8: 00431021 addu r2,r2,r3			#r2 = 0x8004e9d4 + r8 + r4 
000444ac: a0470000 sb r7,0x0000(r2)			#store largest value + 1 to all bytes equal to and larger than the encountered number's address, ignores ones before
000444b0: 24840001 addiu r4,r4,0x0001			#loop count
000444b4: 0085102b sltu r2,r4,r5			#set true if not looped r5 times
000444b8: 1440fffa bne r2,r0,0x000444a4		#loop above until all data spaces are filled with 1
000444bc: 00000000 nop
000444c0: 3c038001 lui r3,0x8001
000444c4: 8c630010 lw r3,0x0010(r3)			#loads LBA pointer
000444c8: 000812c0 sll r2,r8,0x0b			#r2 = r8 << 0xb
000444cc: 00431021 addu r2,r2,r3			#r2 + 801df000 + 0x800 * (largest encountered number + 1)
000444d0: 27bd0008 addiu r29,r29,0x0008
000444d4: 03e00008 jr r31
000444d8: 00000000 nop