Add help

src/args.S

@@ -1,10 +1,8 @@
 .data
 sp_start:       .space 8
-flag_h:         .asciz "-h"
-flag_helpo:     .asciz "--help"
 
 .section .text
-.globl save_sp, fetch_argc, fetch_argv
+.globl save_sp, fetch_argc, fetch_argv, has_switch
 
 save_sp:
     sd sp, sp_start, t0 # save the stack pointer
@@ -94,6 +92,99 @@ fetch_argv:
     addi sp, sp, 8
     ret
 
+# Check if flag was given
+# @param[in] a0: ptr to null-terminated switch 1 (ie. -h).
+# @param[in] a1: ptr to null-terminated switch 2 (ie. --help) (optional).
+# @param[out] a0: result code.
+# @param[out] a1: was found (0-not found, 1-found).
+has_switch:
+    addi sp, sp, -24 # store ra and s regs to stack
+    sd ra, 16(sp)
+    sd s1, 8(sp)
+    sd s0, 0(sp)
+
+    mv s0, a0
+    mv s1, a1
+
+    call fetch_argc
+    bnez a0, 1f
+    li t0, 2
+    blt a1, t0, 1f # if we have no commands other than the binary, we know there will be no switches
+
+    addi sp, sp, -24
+    sd s4, 16(sp)
+    sd s2, 8(sp)
+    sd s3, 0(sp)
+    li s2, 1 # load first non-base command arg
+    mv s4, a1 # put argc in s4
+    
+    2:
+    mv a0, s2
+    call fetch_argv
+    mv s3, a1 # save argv buff addr
+    
+    mv a0, s3 # load argv buff addr into a0 (string 0)
+    mv a1, s0 # move switch ptr 1 addr into a1 (string 1)
+    call _str_cmp
+    bnez a1, 5f # if the strings match, exit loop
+
+    mv a0, s3 # move argv buff addr into a0 (string 0)
+    mv a1, s1 # move switch ptr 2 addr into a1 (string 1)
+    call _str_cmp
+    bnez a1, 5f # if the strings match, exit loop
+
+    addi s2, s2, 1 # if string doesn't match we inc to the next arg
+    blt s2, s4, 2b # keep going while we have untested args
+    
+    4:
+    li a0, 0
+    li a1, 0
+    j 3f
+
+    5:
+    li a0, 0
+    li a1, 1
+
+    3:
+    ld s3, 0(sp)
+    ld s2, 8(sp)
+    ld s4, 16(sp)
+    addi sp, sp, 24
+
+    1:
+    ld ra, 16(sp)
+    ld s1, 8(sp)
+    ld s0, 0(sp)
+    addi sp, sp, 24 # restore ra and s regs from stack
+    ret
+
+# Compares two null terminated string buffers.
+# @param[in] a0: str buffer 1
+# @param[in] a1: str buffer 2
+# @param[out] a0: result code.
+# @param[out] a1: is equal (0-no, 1-yes).
+_str_cmp:
+    li t2, 0
+
+    1:
+    add t0, a0, t2
+    add t1, a1, t2
+    lb t0, 0(t0)
+    lb t1, 0(t1)
+    bne t0, t1, 3f # first byte that isn't the same, branch to no match
+    beqz t0, 2f # jump to ret when null is read
+    addi t2, t2, 1
+    j 1b
+    
+    3: # no match
+    li a0, 0
+    li a1, 0
+    ret
+
+    2: # match
+    li a0, 0
+    li a1, 1
+    ret
 
 # Fetch argument value
 # @param[in] a0: address of current argv.

src/file.S

@@ -2,7 +2,7 @@
 cat_buf:    .space 4096
 
 .section .text
-.globl cat_file, open_fd, file_exists
+.globl cat_file, open_fd
 
 # Cat out the given file to stdout
 # @param[in] a0: ptr to null-terminated file str.

src/main.S

@@ -1,10 +1,20 @@
 .data
 argc:           .space 8
+
 cat_prefix:     .asciz "cat: "
 .equ CAT_PREFIX_LEN, . - cat_prefix
+
 file_err:       .asciz ": No such file or directory\n"
 .equ FILE_ERR_LEN, . - file_err
 
+help:           .asciz "Usage: cat [OPTION]... [FILE]...\nConcatenate FILE(S) to standard output.\n"
+.equ HELP_LEN, . - help
+
+flag_h:         .asciz "-h"
+# .equ FLAG_H_LEN, . - flag_h
+flag_help:     .asciz "--help"
+# .equ FLAG_HELP_LEN, . - flag_help
+
 
 .section .text
 .globl _start
@@ -18,10 +28,20 @@ _start:
     call save_sp
     call fetch_argc
     li t0, 1
-    ble a1, t0, 1f # return 1 if no file given
+    ble a1, t0, 1f # return 1 if no args
     mv s0, a1 # store argc
     li s1, 1
 
+    la a0, flag_h
+    la a1, flag_help
+    call has_switch
+    bnez a0, 1f
+    beqz a1, .Lskip_disp_help
+    call _disp_help
+    j 2f
+    .Lskip_disp_help:
+    
+
     # 5: #iterate through and check that all files exist first
     # mv a0, s1
     # call fetch_argv
@@ -75,3 +95,11 @@ _start:
     li a0, 0
     li a7, 93
     ecall   # return 0
+
+_disp_help:
+    la a0, 1
+    la a1, help
+    li a2, HELP_LEN
+    li a7, 64
+    ecall
+    ret