Converting MIPS assembly to C - c

Question

I am working on converting MIPS to C, and I've been stuck on this for several days.
I've started with manually converting MIPS to C, and even though I've been working on it for several days, my resulting program in C still doesn't run as needed, and I feel like there is a small mistake that I overlooked, and I would really appreciate your help.
I started conversion with toplevel_fnc, and then with subroutine_fnc.
Here is a part of the MIPS code.
Subroutine:
build/program-mips: file format elf32-tradbigmips
Disassembly of section my_text:
00404ed0 <subroutine_fnc>:
404ed0: 27bdffd8 addiu sp,sp,-40
404ed4: afbe0024 sw s8,36(sp)
404ed8: 03a0f025 move s8,sp
404edc: afc40028 sw a0,40(s8)
404ee0: 8fc40028 lw a0,40(s8)
404ee4: 27c20018 addiu v0,s8,24
404ee8: 00402825 move a1,v0
404eec: 24060001 li a2,1
404ef0: 24020fa3 li v0,4003
404ef4: 0000000c syscall
404ef8: afc70008 sw a3,8(s8)
404efc: afc2000c sw v0,12(s8)
404f00: 8fc20008 lw v0,8(s8)
404f04: 00000000 nop
404f08: 14400004 bnez v0,404f1c <subroutine_fnc+0x4c>
404f0c: 00000000 nop
404f10: 8fc2000c lw v0,12(s8)
404f14: 10000002 b 404f20 <subroutine_fnc+0x50>
404f18: 00000000 nop
404f1c: 2402ffff li v0,-1
404f20: afc20010 sw v0,16(s8)
404f24: 8fc20010 lw v0,16(s8)
404f28: 00000000 nop
404f2c: 04410006 bgez v0,404f48 <subroutine_fnc+0x78>
404f30: 00000000 nop
404f34: 24040001 li a0,1
404f38: 24020fa1 li v0,4001
404f3c: 0000000c syscall
404f40: afc70008 sw a3,8(s8)
404f44: afc20014 sw v0,20(s8)
404f48: 8fc20010 lw v0,16(s8)
404f4c: 00000000 nop
404f50: 14400004 bnez v0,404f64 <subroutine_fnc+0x94>
404f54: 00000000 nop
404f58: 00001025 move v0,zero
404f5c: 10000002 b 404f68 <subroutine_fnc+0x98>
404f60: 00000000 nop
404f64: 83c20018 lb v0,24(s8)
404f68: 03c0e825 move sp,s8
404f6c: 8fbe0024 lw s8,36(sp)
404f70: 27bd0028 addiu sp,sp,40
404f74: 03e00008 jr ra
404f78: 00000000 nop
and toplevel:
00404f7c <toplevel_fnc>:
404f7c: 27bdffc0 addiu sp,sp,-64
404f80: afbf003c sw ra,60(sp)
404f84: afbe0038 sw s8,56(sp)
404f88: 03a0f025 move s8,sp
404f8c: afc00018 sw zero,24(s8)
404f90: 10000040 b 405094 <toplevel_fnc+0x118>
404f94: 00000000 nop
404f98: 83c30034 lb v1,52(s8)
404f9c: 2402005c li v0,92
404fa0: 14620022 bne v1,v0,40502c <toplevel_fnc+0xb0>
404fa4: 00000000 nop
404fa8: 8fc20018 lw v0,24(s8)
404fac: 00000000 nop
404fb0: 24420001 addiu v0,v0,1
404fb4: afc20018 sw v0,24(s8)
404fb8: 24040001 li a0,1
404fbc: 3c020041 lui v0,0x41
404fc0: 244260e0 addiu v0,v0,24800
404fc4: 00402825 move a1,v0
404fc8: 24060002 li a2,2
404fcc: 24020fa4 li v0,4004
404fd0: 0000000c syscall
404fd4: afc7001c sw a3,28(s8)
404fd8: afc20020 sw v0,32(s8)
404fdc: 8fc2001c lw v0,28(s8)
404fe0: 00000000 nop
404fe4: 14400004 bnez v0,404ff8 <toplevel_fnc+0x7c>
404fe8: 00000000 nop
404fec: 8fc20020 lw v0,32(s8)
404ff0: 10000002 b 404ffc <toplevel_fnc+0x80>
404ff4: 00000000 nop
404ff8: 2402ffff li v0,-1
404ffc: afc20024 sw v0,36(s8)
405000: 8fc20024 lw v0,36(s8)
405004: 00000000 nop
405008: 04410022 bgez v0,405094 <toplevel_fnc+0x118>
40500c: 00000000 nop
405010: 24040001 li a0,1
405014: 24020fa1 li v0,4001
405018: 0000000c syscall
40501c: afc7001c sw a3,28(s8)
405020: afc20028 sw v0,40(s8)
405024: 1000001b b 405094 <toplevel_fnc+0x118>
405028: 00000000 nop
40502c: 24040001 li a0,1
405030: 27c20034 addiu v0,s8,52
405034: 00402825 move a1,v0
405038: 24060001 li a2,1
40503c: 24020fa4 li v0,4004
405040: 0000000c syscall
405044: afc7001c sw a3,28(s8)
405048: afc2002c sw v0,44(s8)
40504c: 8fc2001c lw v0,28(s8)
405050: 00000000 nop
405054: 14400004 bnez v0,405068 <toplevel_fnc+0xec>
405058: 00000000 nop
40505c: 8fc2002c lw v0,44(s8)
405060: 10000002 b 40506c <toplevel_fnc+0xf0>
405064: 00000000 nop
405068: 2402ffff li v0,-1
40506c: afc20024 sw v0,36(s8)
405070: 8fc20024 lw v0,36(s8)
405074: 00000000 nop
405078: 04410006 bgez v0,405094 <toplevel_fnc+0x118>
40507c: 00000000 nop
405080: 24040001 li a0,1
405084: 24020fa1 li v0,4001
405088: 0000000c syscall
40508c: afc7001c sw a3,28(s8)
405090: afc20030 sw v0,48(s8)
405094: 00002025 move a0,zero
405098: 0c1013b4 jal 404ed0 <subroutine_fnc>
40509c: 00000000 nop
4050a0: 00021600 sll v0,v0,0x18
4050a4: 00021603 sra v0,v0,0x18
4050a8: a3c20034 sb v0,52(s8)
4050ac: 83c20034 lb v0,52(s8)
4050b0: 00000000 nop
4050b4: 1c40ffb8 bgtz v0,404f98 <toplevel_fnc+0x1c>
4050b8: 00000000 nop
4050bc: 8fc20018 lw v0,24(s8)
4050c0: 03c0e825 move sp,s8
4050c4: 8fbf003c lw ra,60(sp)
4050c8: 8fbe0038 lw s8,56(sp)
4050cc: 27bd0040 addiu sp,sp,64
4050d0: 03e00008 jr ra
4050d4: 00000000 nop
program data
build/program-mips: file format elf32-tradbigmips
Contents of section my_data:
4160e0 5c5c0000 \\..
and I wrote it in C as:
int toplevel_fnc(void) {
int a = 0;
while(1) {
char c = subroutine_fnc(0);
if (c <= 0) {
return a;
}
if (c == 92) {
a++;
int d = write(1, "\\", 2);
if (d < 0) {
exit(1);
}
} else {
int e = write(1, &c, 1);
if (e < 0) {
exit(1);
}
}
}
return a;
}
and
int subroutine_fnc(int a) {
char c;
int b = read(a, &c, 1);
if (b < 0) {
exit(1);
} else if (b == 0) {
return 0;
}
return c;
}
I am feeling lost, and also kind of stupid for asking here, but I feel like there is a small mistake that I overlooked. I've been working on this for the past three days, and I can't find the solution on how to correctly convert MIPS to C.
Please, I would be very glad if anyone could help me out on what is wrong in my code.
Thank you.

Answer 1

The assembly program writes two backslashes, whereas the C write(1, "\\", 2) writes one backslash and one NUL, because \\ in a string literal denotes only one backslash; you meant to write(1, "\\\\", 2).
The char is unsigned - this makes another deviation, since at a place in the assembly program a byte is sign extended and later tested with bgtz, while in the C code
char c = subroutine_fnc(0);
if (c <= 0)
the if condition will be true only for c = 0. Use signed char c … instead.