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trønderen wrote:

If I were given the responsibility for a state machine implementation like that, I would immediately run to my boss asking for permission to rewrite the whole thing as a table driven machine.

#include <stdio.h>
#include <conio.h>

// Fn ptrs defs
typedef  void (*RT)( int input );
typedef  RT (*TER)( int input );

// Forward declarations
extern TER state1( int input );
extern TER state2( int input );
extern TER state3( int input );

// First state
TER state1( int input )
{
    printf( "one\t" );
    return input < 10 ? (TER)&state2 : (TER)NULL;
}

// Second state
TER state2( int input )
{
	printf( "two\t" );
	return (TER)&state3;
}

// Third state
TER state3( int input )
{
    printf( "three\t" );
    return (TER)&state1;
}

int main(int argc, char* argv[])
{
    int n;

    // Set Start state
    TER state = (TER)&state1;

    // Exercises the state machine. Ends when state == NULL
    for ( n = 0 ; state ; ++n ) {
        // Executes the current state (state variable) then goes to the next state
        state = (TER)( state( n ) );
    }

    printf( "\n\nPress any key\n" );
    getch();

	return 0;
}

honey the codewitch wrote:

with impossible to follow pointer arrays

honey the codewitch wrote:

I hate function pointer dispatch code in general.

Because at some point you'll have to debug and maintain it, and you end up with impossible to follow pointer arrays hiding the flow of your app.

honey the codewitch wrote:

at some point you'll have to debug and maintain it

honey the codewitch wrote:

I clearly misunderstood you. Sorry.

string json = """
{
  "test": 0,
  "data": "value"
}
""";

JsonStringRunner runner = new();

List<FAMatch> matches = new();
FAMatch current = default;
Stopwatch sw = new();
sw.Start();
do{
    current = runner.GetMatch(json);
    matches.Add(current);
} while(!runner.isDone);
sw.Stop();
matches.Dump();
sw.Dump();

internal record struct FAMatch(int token, string match, int position, int length, int column)
{
    internal static FAMatch Create(int token, string match, int position, int length, int column)
        => new(token, match, position, length, column);
}

internal abstract class FAStringRunner
{
    protected int position = -1, line = 0, column = 0;
    internal bool isDone = false;
}

internal sealed partial class JsonStringRunner : FAStringRunner
{
    private void Advance(string s, ref int ch, ref int len, bool flag)
    {
        // Assuming Advance takes consecutive characters in the string.
        ch = s[position];
        position++;
        len++;
        isDone = !(position < s.Length);
    }
    private FAMatch NextMatchImpl(string s)
    {
        int ch;
        int len;
        int l;
        int c;
        ch = -1;
        len = 0;
        if ((this.position is -1))
        {
            this.position = 0;
        }
        int p = this.position;
        l = this.line;
        c = this.column;
        this.Advance(s, ref ch, ref len, true);
        // q0:
        switch (ch)
        {
            // [\t-\n\r ]
            case 9 or 10 or 13 or 32:
                if(ch is 10 or 13){
                    l = line++;
                }
                return q1();
            // [\"]
            case 34:
                return q2();
            // [,]
            case 44:
                return q9();
            // [\-]
            case 45:
                return q10();
            // [0]
            case 48:
                return q11();
            // [1-9]
            case >= 49 and <= 57:
                return q17();
            // [\:]
            case 58:
                return q18();
            // [\[]
            case 91:
                return q19();
            // [\]]
            case 93:
                return q20();
            // [f]
            case 102:
                return q21();
            // [n]
            case 110:
                return q26();
            // [t]
            case 116:
                return q30();
            // [\{]
            case 123:
                return q32();
            // [\}]
            case 125:
                return q33();
        }
        return errorout();

        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q1()
        {
            // [\t-\n\r ]
            while (ch is 9 or 10 or 13 or 32)
            {
                this.Advance(s, ref ch, ref len, false);
            }
            return FAMatch.Create(10, s.Substring(p, len), p, l, c);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q2()
        {
            // [\0-\t\v-!#-\[\]-\x10ffff]
            while (ch is (((((>= 0)
                        and (<= 9))
                        or ((>= 11)
                        and (<= 33)))
                        or ((>= 35)
                        and (<= 91)))
                        or ((>= 93)
                        and (<= 1114111))))
            {
                this.Advance(s, ref ch, ref len, false);
            }
            // [\"]
            if ((ch is 34))
            {
                this.Advance(s, ref ch, ref len, false);
                return q3();
            }
            // [\\]
            if ((ch is 92))
            {
                this.Advance(s, ref ch, ref len, false);
                return q4();
            }

            return default;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q3() => FAMatch.Create(9, s.Substring(p, len), p, l, c);

        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q4()
        {
            // [\"\/\\bfnrt]
            if (ch is 34 or 47
                        or 92
                        or 98
                        or 102
                        or 110
                        or 114
                        or 116)
            {
                this.Advance(s, ref ch, ref len, false);
                return q2();
            }

            // [u]
            if (ch is 117)
            {
                this.Advance(s, ref ch, ref len, false);
                return q5();
            }

            return errorout();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q5()
        {
            // [0-9A-Fa-f]
            if (ch is (>= 48 and <= 57) or (>= 65 and <= 70)
                        or (>= 97 and <= 102))
            {
                this.Advance(s, ref ch, ref len, false);
                return q6();
            }
            return errorout();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q6()
        {
            // [0-9A-Fa-f]
            if (ch is (>= 48 and <= 57) or (>= 65 and <= 70)
                        or (>= 97 and <= 102))
            {
                this.Advance(s, ref ch, ref len, false);
                return q7();
            }
            return errorout();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q7() => FAMatch.Create(7, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q9() => FAMatch.Create(9, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q10() => FAMatch.Create(10, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q11() => FAMatch.Create(11, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q17() => FAMatch.Create(17, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q18() => FAMatch.Create(18, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q19() => FAMatch.Create(19, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q20() => FAMatch.Create(20, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q21() => FAMatch.Create(21, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q26() => FAMatch.Create(26, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q30() => FAMatch.Create(110, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q32() => FAMatch.Create(123, s.Substring(p, len), p, l, c);
        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch q33() => FAMatch.Create(125, s.Substring(p, len), p, l, c);

        [MethodImpl(MethodImplOptions.AggressiveInlining)] FAMatch errorout() => FAMatch.Create(0, s.Substring(p, len), p, l, c); // Dunno what you do in this section of code.
    }

    public FAMatch GetMatch(string s) => NextMatchImpl(s);
}

if (match[ch])
...

honey the codewitch wrote:

if (((((ch >= 9)
&& (ch <= 10))
|| (ch == 13))
|| (ch == 32))) {

(ch == 9) || (ch == 10) || (ch == 13) || (ch == 32))