Specific RLE encoding, 2 bytes run + conditions 00, LF, rare format

Question

I'm new to coding in c. I want to decode RLE encoded binary files (vintage, rare pic format) with these conditions:

character, followed by number of characters

run count is valid for counts >=4

0 is encoded 00 00

1 is encoded 00 01

10 (hex ?) is LF

EOF is encoded as 00 03

bottom byte (after EOF is 0A)

there's a 2 byte count: , 4<=<=127 , >8> ! 128, &255, examples

0 1 2 3 4 5 encodes as 0 0 1 2 3 4 5 encode 0 as 0,0

5 6 7 8 9 10 encodes as 5 6 7 8 9 0 1 encode 10 as 0,1

5...(200 times) encodes as 5 0 128 200 long repeat count of 200

7...(515 times) encodes as 7 0 130 3 long repeat count of 16_203

The file format is complicated and includes:

variable header length (512/1024 bytes) different compressions, including different RLE compressions (horizontal, vertical) variable color maps (variable lengths) and none, stereo pics, CAD pics, fractals, geosat pics, etc, but for now I just want to decode headerless data.

I searched a lot for RLE here and elsewhere and tried for some days but there are mainly threads about strings and none about selected conditions like for character 0 etc. And especially for checking 3 Bytes.

I have documents and codes in 2 older languages including Assembler. I found here a similar code in c++ but I couldn't translate it properly. I managed to make some c programs without compiling errors, but the result is wrong.

The best code is below. It reads multiple bytes but missing some "00" bytes. Bytes 1+3 are correct. Byte 2 is 0, Byte 4 missing. The output to file is completely wrong and just 3 bytes. Even the 1st byte is wrong. (80)
I'm confused reading 3 bytes with 2 variables. Byte flipping? Can anybody help? Thanks!

while (!feof(fp1))
    {              //originally also have to check if 1st char=10 (LF) and overrides that 
         if(fread(buf,1,2,fp1)!=2) //Read two bytes: original code was number of characters + characters
                  // but I have characters + number of ch, and more conditions    
             
            continue; // was break;
        ch = buf[0]; //was num ch instead of ch, also swapped below at buf 1
        printf("%x\n", ch); //later added this to output to screen, reads more than output but bytes like 0 missing
          if(ch==0) {
                if(ch==1) {
                ch=10;        // code for LF    
                continue;         // is this correct?  continue or return (0) or -1? same below
           }else{    
                if(ch==0) {
                ch=0;         // 00 00 encoded as 0  
                continue;   
           }else{    
                if(ch==3);    //EOF, after that bottom byte 0A follows
                return (0);   
                }   
           }                  //else beep? return -1, break, but I rely on proper image not having 00 04...
          }
    }
        num = buf[1];
        char * chbuf = (char *)malloc(num);   
                                          //main code from_WRITE IMAGE, although read
            if(num==1) {        // no action               v----------v-----------v-------
            } else if (num<4) {   // run counts only when count =>4    
                
             for (int i =0;i < num;i++)   
                 chbuf[i] = ch;
             fwrite(&chbuf,1,num,fp2);        //num ? ,1? or 0    was fwrite(chbuf
             }else if (num<=127); {
             for (int i =0;i < num;i++)                     
                  chbuf[i] = num;               ////newest added is this right?
            if (num==10) {      
            fwrite(&chbuf,1,num,fp2); //num--;   //num ?, or is it ch or char or i?
           }else {
           if ((ch&255)==10) {                 // was num&, I tried all, num and ch , always wrong 
           num++;    
           fwrite(&chbuf,1,ch,fp2);  // was num--; at end
           num++;                   // is num++ right? but neverless always just 3 bytes
           fwrite(&chbuf,2,((unsigned) num>>8|0x80),fp2); // was chbuf 1, also checked unsigned char, 80, else 
           num++;
           fwrite(&chbuf,1,ch,fp2); // was 1
           } 
          }
             }
         free(chbuf);   

New code 3

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//3rd code this time with internal string, code 2 worked (read 2 bytes from file, print to screen) 
int i, j;            //output should be 88 times 05, 4 times 06
int main()
{
        char string[] = "0500580604"; //hex test input to not have external file
                                       //for now no check for conditions like EOF, 00 at begin
        int number1 = atoi(string [0]); //convert string to byte was [1]
        int number2 = atoi(string [1]);
        int number3 = atoi(string [2]);
        if (number2 == 0){        //read byte 2 and check if it's a count, Byte 1 is a char
            if (number2 >=4){     //check byte 2 if valid count or char
            }else {printf("%x\n", number1, number2); //byte 2 is a char 
        } return (0);
            if (number3<127){ //check byte 3 if its a long run
                for (int i =0;i < number2;i++) // print byte2 times the char   
                printf("%x\n", number1);
            }else {
            for (int i =0;i <number3;i++) //print byte3 times the char
            printf("%x\n", number1);
           return (0); 
            }
           }
          }