// Ary/Vector of u8s - a resizable array of bytes.
struct aryu8 {
    u32 !len = 0;
    u8[] !buf;

    new aryu8 = { -> buf = new u8[1]; };

    // Grow as needed
    val _grow = { u32 len2 ->
        if( len+len2 <= buf# ) return self;
        u32 newlen = ary.capacity(buf#,len+len2);
        if( !newlen ) libc._exit(1); // Length exceeds the array representation.
        u8[] !buf2 = new u8[newlen];
        ary.copy(buf2,0,buf,0,len);
        buf = buf2;
        self;
    };

    val clear = { -> len = 0; self; };

    // Add a character to aryu8
    val add = { u8 c ->
        _grow(1).buf[len++] = c;
        self;
    };

    // Add all of a plain array to the aryu8
    val addAry = { u8[~] xs ->
        u32 n=xs#;
        _grow(n);
        ary.copy(buf,len,xs,0,n);
        len += n;
        self;
    };

    // Remove x bytes from the tail.
    val undo = { u32 x ->
        len = len >= x ? len-x : 0;
        self;
    };

    // Print ASCII number into aryu8
    val num = { i64 x ->
        text.integer(self,x,0,0,-1);
        self;
    };

    // Write all bytes to fd; return len, or -1 with errno set on failure.
    val write = { i32 fd ->
        io.writeOff(fd,buf,0,len);
    };
};


// Parse one integer, ignore trailing data; returns 0 with an empty string.
// If you want a more robust parsing, use the `scan` class
val atoi = { u8[~] str ->
    u32 x = 0;
    while( x < str# && str[x] <= ' ' ) x++;
    if( x == str# ) return 0;
    bool neg = false;
    if( str[x]=='-' ) { neg=true; x++; }
    i64 n = 0;
    while( x < str# && '0' <= str[x] <= '9' )
        n = n*10 + str[x++]-'0';
    return neg ? -n : n;
};

// Zero-terminate a string for libc, reserving one array element for the zero.
{ u8[~] -> u8[] } str0 = { u8[~] str ->
  if( str# == 4294967295 ) libc._exit(1);
  u8[] !strz = new u8[str#+1];
  u32 len=str#;
  ary.copy(strz,0,str,0,len);
  strz[str#] = '\0';
  strz;
};