Verification required (dodgy programmer @ work)

[StainlessS]

Hi guys, just need some assurance that I'm not doing anything terribly sinful in the plug I'm putting together, the possibly
problematic bit concerns returning a string to Avisynth and handing over management of it.
The code of concern is hi-lited, the rest is still a work in progress and need not attract comment.
Also, Am I correct in thinking that the env->SaveString func makes a copy of the string and returns the new memory buffer
to the caller which can then be handed back to Avisynth and the
original buffer freed.
I would appreciate some feedback on this as stoney silence is not very reassuring.

Here's the code as it currently stands:

AVSValue __cdecl Create_RT_ReadTxtFromFile(AVSValue args, void* user_data, IScriptEnvironment* env) {
    enum{BFSZ=512};
    char bf[BFSZ+2];                                                        // with a little spare
    const char *filename=args[0].AsString();
    int Lines=args[1].AsInt(0);                                             // Allow user set default=0
    FILE *fp;   
    unsigned char c,*p,*s,*pbf;
    long flen,chk,wr,line;
    if(!(fp = fopen(filename, "r"))) {env->ThrowError("RT_ReadTxtFromFile: Cannot Open file %s",filename);} 
    if((fseek(fp, 0, SEEK_END)!=0) || ((flen=ftell(fp)) == -1L)) { fclose(fp);
        env->ThrowError("RT_ReadTxtFromFile: Cannot seek in file %s",filename);}
    rewind(fp);
    if ((chk=3)>flen)   chk=flen;
    if(chk==0) { fclose(fp); bf[0]=0; return env->SaveString(bf);}          // Return "" to Avisynth
    wr = fread(bf, 1, chk, fp);
    if(wr != chk) {fclose(fp);env->ThrowError("RT_ReadTxtFromFile: Cannot read from file %s",filename);}
    if(chk==3 && bf[0]==0xEF && bf[1]==0xBB && bf[2]==0xBF) {
        fclose(fp); env->ThrowError("RT_ReadTxtFromFile: UTF-8 text files are not supported, "
        "re-save with ANSI encoding! : '%s'", filename);}
    if((chk>=2 && ((bf[0]==0xFF && bf[1]==0xFE) || (bf[0]==0xFE && bf[1]==0xFF)))) {
        fclose(fp); env->ThrowError("RT_ReadTxtFromFile: UTF-8 text files are not supported, "
        "re-save with ANSI encoding! : '%s'", filename);}
    rewind(fp);
    if((pbf = new unsigned char[flen])==NULL)
        {fclose(fp); env->ThrowError("RT_ReadTxtFromFile: Cannot allocate memory for %s",filename);}
    p=pbf;
    if(Lines <= 0) Lines = 0x7FFFFFFF;
    line = 0;
    while(line < Lines && (fgets(bf, BFSZ,fp ) != NULL)) {                  // will halt at first Nul byte if bin file
        ++line;
        s = (unsigned char *)bf;                                            // start of input buffer
        while(c = *s) {
            if(c>=' ' && c <= 126) {                                        // All ASCII printable incl SPACE
                *p++=c;
            } else if(c=='\n' || c=='\r') {
                *p++='\n';                                                  // Output single '\n'
                if((c=='\n' && s[1]=='\r') || (c=='\r' &&  s[1]=='\n'))     // Allow skip of matched pairs CR/LF or LF/CR
                    ++s;                                                    // Skip to 1st of match pair EOL
            } else { // Just allow control codes and non Ascii through, maybe change in future, perhaps user selectable
                *p++ = c;                                                   
            }
            ++s;                                                            // Next char in input buffer
        }
    }           
    *p='\0';                                                                // Nul term sentinel
    fclose(fp);
    AVSValue ret =  env->SaveString((const char*)pbf);                      // Get pointer to Avisynth saved string
    delete [] pbf;                                                          // Delete original buffer
    return ret;                                                             // Return Avisynth's copy to Avisynth
}

EDITED:

and the calling script

TS=RT_ReadTxtFromFile("D:\avs\bank\mcdegrain.avs")
RT_debug(TS)
TS="" # Hopefully this will deallocate the string.
EDIT: This would have been a better choice: TS=0

And the output in RT_Stats RT_Debug()

00000004  02:32:34  RT_Debug: 
00000005  02:32:34  RT_Debug: Function MCDegrain(clip c, int "frames")  
00000006  02:32:34  RT_Debug: { # By Didee, http://forum.doom9.org/showthread.php?p=1508289#post1508289 
00000007  02:32:34  RT_Debug: 
00000008  02:32:34  RT_Debug: frames = default(frames, 2) 
00000009  02:32:34  RT_Debug: bs = (c.width>960) ? 16 : 8 
00000010  02:32:34  RT_Debug: super = c.MSuper(pel=2, sharp=1)  
00000011  02:32:34  RT_Debug: backward_vec3 = MAnalyse(super, isb = true, delta = 3, blksize=bs, overlap=bs/2)  
00000012  02:32:34  RT_Debug: backward_vec2 = MAnalyse(super, isb = true, delta = 2, blksize=bs, overlap=bs/2)  
00000013  02:32:34  RT_Debug: backward_vec1 = MAnalyse(super, isb = true, delta = 1, blksize=bs, overlap=bs/2)  
00000014  02:32:34  RT_Debug: forward_vec1 = MAnalyse(super, isb = false, delta = 1, blksize=bs, overlap=bs/2)  
00000015  02:32:34  RT_Debug: forward_vec2 = MAnalyse(super, isb = false, delta = 2, blksize=bs, overlap=bs/2)  
00000016  02:32:34  RT_Debug: forward_vec3 = MAnalyse(super, isb = false, delta = 3, blksize=bs, overlap=bs/2)  
00000017  02:32:34  RT_Debug: (frames<=0) ? c :\  
00000018  02:32:34  RT_Debug: (frames==1) ? c.MDegrain1(super, backward_vec1,forward_vec1,thSAD=400) :\ 
00000019  02:32:34  RT_Debug: (frames==2) ? c.MDegrain2(super, backward_vec1,forward_vec1,backward_vec2,forward_vec2,thSAD=400) :\  
00000020  02:32:34  RT_Debug:      c.MDegrain3(super, backward_vec1,forward_vec1,backward_vec2,forward_vec2,backward_vec3,forward_vec3,thSAD=400) 
00000021  02:32:34  RT_Debug: return(last)  
00000022  02:32:34  RT_Debug: } 
00000023  02:32:34  RT_Debug: 
00000024  02:32:34  RT_Debug: Function MCDegrainSharp(clip c, int "frames", float "bblur", float "csharp", bool "bsrch")  
00000025  02:32:34  RT_Debug: { # Based on MCDegrain By Didee, http://forum.doom9.org/showthread.php?t=161594 
00000026  02:32:34  RT_Debug:  # Also based on DiDee observations in this thread: http://forum.doom9.org/showthread.php?t=161580  
00000027  02:32:34  RT_Debug:  # "Denoise with MDegrainX, do slight sharpening where motionmatch is good, do slight blurring where motionmatch is bad"  
00000028  02:32:34  RT_Debug:  # In areas where MAnalyse cannot find good matches, the blur() will be dominant. 
00000029  02:32:34  RT_Debug:  # In areas where good matches are found, the sharpen()'ed pixels will overweight the blur()'ed pixels  
00000030  02:32:34  RT_Debug:  # when the pixel averaging is performed.   
00000031  02:32:34  RT_Debug: frames = default(frames, 2) 
00000032  02:32:34  RT_Debug: bblur  = default(bblur, 0.6)  
00000033  02:32:34  RT_Debug: csharp = default(csharp, 0.6) 
00000034  02:32:34  RT_Debug: bsrch  = default(bsrch, true) 
00000035  02:32:34  RT_Debug: bs = (c.width>960) ? 16 : 8 
00000036  02:32:34  RT_Debug: 
00000037  02:32:34  RT_Debug: c2 = c.blur(bblur)  
00000038  02:32:34  RT_Debug: super = bsrch ? c2.MSuper(pel=2, sharp=1) : c.MSuper(pel=2, sharp=1)  
00000039  02:32:34  RT_Debug: super_rend = c.sharpen(csharp).MSuper(pel=2, sharp=1,levels=1)  
00000040  02:32:34  RT_Debug: backward_vec3 = MAnalyse(super, isb = true, delta = 3, blksize=bs, overlap=bs/2)  
00000041  02:32:34  RT_Debug: backward_vec2 = MAnalyse(super, isb = true, delta = 2, blksize=bs, overlap=bs/2)  
00000042  02:32:34  RT_Debug: backward_vec1 = MAnalyse(super, isb = true, delta = 1, blksize=bs, overlap=bs/2)  
00000043  02:32:34  RT_Debug: forward_vec1 = MAnalyse(super, isb = false, delta = 1, blksize=bs, overlap=bs/2)  
00000044  02:32:34  RT_Debug: forward_vec2 = MAnalyse(super, isb = false, delta = 2, blksize=bs, overlap=bs/2)  
00000045  02:32:34  RT_Debug: forward_vec3 = MAnalyse(super, isb = false, delta = 3, blksize=bs, overlap=bs/2)  
00000046  02:32:34  RT_Debug: (frames<=0) ? c :\  
00000047  02:32:34  RT_Debug: (frames==1) ? c2.MDegrain1(super_rend, backward_vec1,forward_vec1,thSAD=400) :\ 
00000048  02:32:34  RT_Debug: (frames==2) ? c2.MDegrain2(super_rend, backward_vec1,forward_vec1,backward_vec2,forward_vec2,thSAD=400) :\  
00000049  02:32:34  RT_Debug:      c2.MDegrain3(super_rend, backward_vec1,forward_vec1,backward_vec2,forward_vec2,backward_vec3,forward_vec3,thSAD=400) 
00000050  02:32:34  RT_Debug: return(last)  
00000051  02:32:34  RT_Debug: } 
00000052  02:32:34  RT_Debug: 
00000053  02:32:34  RT_Debug:

The New plug is to read in a text file and return it in a string,
and work being done on RT_Debug, will parse a string for EOL codes and output to OutputDebugString.

EDIT:
RT_Stats v1.02, below of from mediafire account in sig:
http://forum.doom9.org/showthread.php?t=165479
EDIT: Above link fixed.