https://github.com/akkartik/mu/blob/main/411string.mu

      1 # read up to 'len' graphemes after skipping the first 'start' ones
      2 fn substring in: (addr array byte), start: int, len: int, out-ah: (addr handle array byte) {
      3   var in-stream: (stream byte 0x100)
      4   var in-stream-addr/esi: (addr stream byte) <- address in-stream
      5   write in-stream-addr, in
      6   var out-stream: (stream byte 0x100)
      7   var out-stream-addr/edi: (addr stream byte) <- address out-stream
      8   $substring:core: {
      9     # skip 'start' graphemes
     10     var i/eax: int <- copy 0
     11     {
     12       compare i, start
     13       break-if->=
     14       {
     15         var dummy/eax: grapheme <- read-grapheme in-stream-addr
     16         compare dummy, 0xffffffff/end-of-file
     17         break-if-= $substring:core
     18       }
     19       i <- increment
     20       loop
     21     }
     22     # copy 'len' graphemes
     23     i <- copy 0
     24     {
     25       compare i, len
     26       break-if->=
     27       {
     28         var g/eax: grapheme <- read-grapheme in-stream-addr
     29         compare g, 0xffffffff/end-of-file
     30         break-if-= $substring:core
     31         write-grapheme out-stream-addr, g
     32       }
     33       i <- increment
     34       loop
     35     }
     36   }
     37   stream-to-array out-stream-addr, out-ah
     38 }
     39
     40 fn test-substring {
     41   var out-h: (handle array byte)
     42   var out-ah/edi: (addr handle array byte) <- address out-h
     43   # prefix substrings
     44   substring 0, 0, 3, out-ah
     45   var out/eax: (addr array byte) <- lookup *out-ah
     46   check-strings-equal out, "", "F - test-substring/null"
     47   substring "", 0, 3, out-ah
     48   var out/eax: (addr array byte) <- lookup *out-ah
     49 #?   print-string-to-real-screen out
     50 #?   print-string-to-real-screen "\n"
     51   check-strings-equal out, "", "F - test-substring/empty"
     52   #
     53   substring "abcde", 0, 3, out-ah
     54   var out/eax: (addr array byte) <- lookup *out-ah
     55 #?   print-string-to-real-screen out
     56 #?   print-string-to-real-screen "\n"
     57   check-strings-equal out, "abc", "F - test-substring/truncate"
     58   #
     59   substring "abcde", 0, 5, out-ah
     60   var out/eax: (addr array byte) <- lookup *out-ah
     61   check-strings-equal out, "abcde", "F - test-substring/all"
     62   #
     63   substring "abcde", 0, 7, out-ah
     64   var out/eax: (addr array byte) <- lookup *out-ah
     65   check-strings-equal out, "abcde", "F - test-substring/too-small"
     66   # substrings outside string
     67   substring "abcde", 6, 1, out-ah
     68   var out/eax: (addr array byte) <- lookup *out-ah
     69   check-strings-equal out, "", "F - test-substring/start-too-large"
     70   # trim prefix
     71   substring "", 2, 3, out-ah
     72   var out/eax: (addr array byte) <- lookup *out-ah
     73   check-strings-equal out, "", "F - test-substring/middle-empty"
     74   #
     75   substring "abcde", 1, 2, out-ah
     76   var out/eax: (addr array byte) <- lookup *out-ah
     77   check-strings-equal out, "bc", "F - test-substring/middle-truncate"
     78   #
     79   substring "abcde", 1, 4, out-ah
     80   var out/eax: (addr array byte) <- lookup *out-ah
     81   check-strings-equal out, "bcde", "F - test-substring/middle-all"
     82   #
     83   substring "abcde", 1, 5, out-ah
     84   var out/eax: (addr array byte) <- lookup *out-ah
     85   check-strings-equal out, "bcde", "F - test-substring/middle-too-small"
     86 }
     87
     88 fn split-string in: (addr array byte), delim: grapheme, out: (addr handle array (handle array byte)) {
     89   var in-stream: (stream byte 0x100)
     90   var in-stream-addr/esi: (addr stream byte) <- address in-stream
     91   write in-stream-addr, in
     92   var tokens-stream: (stream (handle array byte) 0x100)
     93   var tokens-stream-addr/edi: (addr stream (handle array byte)) <- address tokens-stream
     94   var curr-stream: (stream byte 0x100)
     95   var curr-stream-addr/ecx: (addr stream byte) <- address curr-stream
     96   $split-string:core: {
     97     var g/eax: grapheme <- read-grapheme in-stream-addr
     98     compare g, 0xffffffff
     99     break-if-=
    100 #?     print-grapheme-to-real-screen g
    101 #?     print-string-to-real-screen "\n"
    102     compare g, delim
    103     {
    104       break-if-!=
    105       # token complete; flush
    106       var token: (handle array byte)
    107       var token-ah/eax: (addr handle array byte) <- address token
    108       stream-to-array curr-stream-addr, token-ah
    109       write-to-stream tokens-stream-addr, token-ah
    110       clear-stream curr-stream-addr
    111       loop $split-string:core
    112     }
    113     write-grapheme curr-stream-addr, g
    114     loop
    115   }
    116   stream-to-array tokens-stream-addr, out
    117 }
    118
    119 fn test-split-string {
    120   var out-h: (handle array (handle array byte))
    121   var out-ah/edi: (addr handle array (handle array byte)) <- address out-h
    122   # prefix substrings
    123   split-string "bab", 0x61, out-ah
    124   # no crash
    125 }