luajitos

stringfix.lua (5128B)

---

 -- stringfix.lua: Pure Lua string function implementations
 -- for bare metal LuajitOS where C string functions cause triple faults
 
 osprint("Loading stringfix.lua...\n")
 
 -- Save the built-in sub function if it exists and works
 local builtin_sub = string.sub
 
 -- Create character/byte lookup tables using only string literals and sub
 local byte_to_char = {}
 local char_to_byte = {}
 
 -- Build lookup using string literals with all ASCII characters
 local ascii = ""
 for i = 0, 255 do
     if i < 32 then
         -- Control characters
         if i == 0 then ascii = ascii .. "\x00"
         elseif i == 1 then ascii = ascii .. "\x01"
         elseif i == 2 then ascii = ascii .. "\x02"
         elseif i == 3 then ascii = ascii .. "\x03"
         elseif i == 4 then ascii = ascii .. "\x04"
         elseif i == 5 then ascii = ascii .. "\x05"
         elseif i == 6 then ascii = ascii .. "\x06"
         elseif i == 7 then ascii = ascii .. "\x07"
         elseif i == 8 then ascii = ascii .. "\x08"
         elseif i == 9 then ascii = ascii .. "\x09"
         elseif i == 10 then ascii = ascii .. "\x0A"
         elseif i == 11 then ascii = ascii .. "\x0B"
         elseif i == 12 then ascii = ascii .. "\x0C"
         elseif i == 13 then ascii = ascii .. "\x0D"
         elseif i == 14 then ascii = ascii .. "\x0E"
         elseif i == 15 then ascii = ascii .. "\x0F"
         elseif i == 16 then ascii = ascii .. "\x10"
         elseif i == 17 then ascii = ascii .. "\x11"
         elseif i == 18 then ascii = ascii .. "\x12"
         elseif i == 19 then ascii = ascii .. "\x13"
         elseif i == 20 then ascii = ascii .. "\x14"
         elseif i == 21 then ascii = ascii .. "\x15"
         elseif i == 22 then ascii = ascii .. "\x16"
         elseif i == 23 then ascii = ascii .. "\x17"
         elseif i == 24 then ascii = ascii .. "\x18"
         elseif i == 25 then ascii = ascii .. "\x19"
         elseif i == 26 then ascii = ascii .. "\x1A"
         elseif i == 27 then ascii = ascii .. "\x1B"
         elseif i == 28 then ascii = ascii .. "\x1C"
         elseif i == 29 then ascii = ascii .. "\x1D"
         elseif i == 30 then ascii = ascii .. "\x1E"
         elseif i == 31 then ascii = ascii .. "\x1F"
         end
     elseif i >= 32 and i < 127 then
         -- Printable ASCII - build from literal string
         local printable = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
         ascii = ascii .. builtin_sub(printable, i - 31, i - 31)
     elseif i == 127 then
         ascii = ascii .. "\x7F"
     else
         -- Extended ASCII - use placeholder
         ascii = ascii .. "?"
     end
 
     -- Build lookup tables
     local ch = builtin_sub(ascii, i + 1, i + 1)
     byte_to_char[i] = ch
     if i < 128 then  -- Only map standard ASCII to avoid collisions
         char_to_byte[ch] = i
     end
 end
 
 osprint("Lookup tables built\n")
 
 -- Override string.byte with pure Lua implementation
 function string.byte(s, i, j)
     i = i or 1
     j = j or i
     local len = #s
 
     -- Handle negative indices
     if i < 0 then i = len + i + 1 end
     if j < 0 then j = len + j + 1 end
 
     -- Clamp to bounds
     if i < 1 then i = 1 end
     if j > len then j = len end
     if i > j then return end
 
     -- Extract bytes
     local results = {}
     for pos = i, j do
         local ch = builtin_sub(s, pos, pos)
         local b = char_to_byte[ch]
         if b then
             results[#results + 1] = b
         else
             -- Unknown character, return '?'
             results[#results + 1] = 63
         end
     end
 
     -- Return multiple values
     if #results == 1 then
         return results[1]
     else
         return table.unpack(results)
     end
 end
 
 -- Override string.char with pure Lua implementation
 function string.char(...)
     local args = {...}
     local result = {}
 
     for i = 1, #args do
         local b = args[i]
         if b < 0 or b > 255 then
             error("bad argument to 'char' (invalid byte value)")
         end
         result[i] = byte_to_char[b] or "?"
     end
 
     return table.concat(result)
 end
 
 osprint("string.byte and string.char overridden\n")
 
 -- Additional string functions using our safe byte/char
 
 function string.charAt(s, i)
     local len = #s
     if i < 0 then i = len + i + 1 end
     if i < 1 or i > len then return "" end
     return builtin_sub(s, i, i)
 end
 
 function string.reverse(s)
     local result = {}
     for i = #s, 1, -1 do
         result[#result + 1] = builtin_sub(s, i, i)
     end
     return table.concat(result)
 end
 
 function string.lower(s)
     local result = {}
     for i = 1, #s do
         local b = string.byte(s, i)
         -- A-Z is 65-90
         if b >= 65 and b <= 90 then
             b = b + 32
         end
         result[#result + 1] = string.char(b)
     end
     return table.concat(result)
 end
 
 function string.upper(s)
     local result = {}
     for i = 1, #s do
         local b = string.byte(s, i)
         -- a-z is 97-122
         if b >= 97 and b <= 122 then
             b = b - 32
         end
         result[#result + 1] = string.char(b)
     end
     return table.concat(result)
 end
 
 osprint("stringfix.lua loaded successfully!\n")