/*********************************************************************

 *   Copyright 2018, UCAR/Unidata

 *   See netcdf/COPYRIGHT file for copying and redistribution conditions.

 *   $Header$

 *********************************************************************/

#include "config.h"

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <assert.h>

#include "ncuri.h"

#include "ncbytes.h"

#include "nclist.h"

/* Include netcdf.h to allow access to

   NC_ error return codes. */

#include "netcdf.h"

#define NCURIDEBUG

/* Extra debug info */

#undef NCXDEBUG

#ifdef NCURIDEBUG

#define THROW(n) {ret=(n); goto done;}

#else

#define THROW(n) {goto done;}

#endif

#define PADDING 8

#define LBRACKET '['

#define RBRACKET ']'

#define EOFCHAR '\0'

#define RBRACKETSTR "]"

#define DRIVELETTERS "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

#ifndef FIX

#define FIX(s) ((s)==NULL?"NULL":(s))

#endif

#ifndef NILLEN

#define NILLEN(s) ((s)==NULL?0:strlen(s))

#endif

#ifndef nulldup

#define nulldup(s) ((s)==NULL?NULL:strdup(s))

#endif

#define terminate(p) {*(p) = EOFCHAR;}

#define endof(p) ((p)+strlen(p))

#define lshift(buf,buflen) {memmove(buf,buf+1,buflen+1);}

#define rshift(buf,buflen) {memmove(buf+1,buf,buflen+1);}

/* Allowable character sets for encode */

static char* ascii = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";

/* Classes according to the URL RFC" */

#define RFCRESERVED " !*'();:@&=+$,/?#[]"

#define RFCUNRESERVED "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.~"

#define RFCOTHER "\"%<>\\^`{|}"

/* I really hate the URL encoding mess */

static const char* pathallow =

"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!#$&'()*+,-./:;=?@_~";

static const char* queryallow =

"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!#$&'()*+,-./:;=?@_~";

/* user+pwd allow = path allow - "@:" */

static const char* userpwdallow =

"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!$&'()*+,-.;=_~?#/";

/* Forward */

static int collectprefixparams(char* text, char** nextp);

static void freestringlist(NClist* list);

static int ncfind(NClist* params, const char* key);

static char* nclocate(char* p, const char* charlist);

static int parselist(const char* ptext, NClist* list);

static int unparselist(const NClist* vec, const char* prefix, int encode, NCbytes*);

static int ensurefraglist(NCURI* uri);

static int ensurequerylist(NCURI* uri);

static void removedups(NClist* list);

/**************************************************/

/*

A note about parameter support:

In the original url format for opendap (dap2), client parameters were

assumed to be one or more instances of bracketed pairs: e.g

    "[...][...]...".

These were assumed to be placed at the front of the url.  In this newer

version, the parameters may be encoded after a trailing # character each

separated by ampersand (&).  For back compatibility, the bracketed

parameter form is supported. However, if ncuribuild is used, all

parameters will be converted to the

    #...&...& format.

In any case, each parameter in turn is assumed to be a of the form

<name>=<value> or <name>; e.g. #x=y&z&a=b&w.

If the same parameter is specified more than once, then the first

occurrence is used; this is so that is possible to forcibly override

user specified parameters by prefixing.

IMPORTANT: the client parameter string is assumed to have blanks compressed out.

*/

/**************************************************/

/* Do a simple uri parse: return NC_NOERR if success, NC_EXXX if failed */

int

ncuriparse(const char* uri0, NCURI** durip)

{

    int ret = NC_NOERR;

    NCURI tmp;

    char* p;

    char* q;

    int isfile;

    int hashost;

    char* uri = NULL;

    NCURI* duri = NULL;

    char* prefix = NULL;

    char* next = NULL;

    NClist* params = nclistnew();

    NClist* querylist = nclistnew();

    size_t len0;

    char pathchar;

    if(uri0 == NULL)

  {THROW(NC_EURL);}

    len0 = strlen(uri0);

    if(len0 == 0)

  {THROW(NC_EURL);}

    /* Create a local NCURI instance to hold

       pointers into the parsed string

    */

    memset(&tmp,0,sizeof(tmp));

    /* make mutable copy. Add some extra space

       because we will need to null terminate the host section

       without losing the first character of the path section.

    */

    uri = (char*)malloc(len0+1+1); /* +2 for nul term and for host section terminator */

    if(uri == NULL)

  {THROW(NC_ENOMEM);}

    /* Safe because we allocated enough space right above (and */

    /* `strdup` isn't usable because we need "one more char"). */

    strcpy(uri,uri0);

    /* Walk the uri and do the following:

  1. remove leading and trailing whitespace

  2. convert all '\\' -> '\' (Temp hack to remove escape characters

                                    inserted by Windows or MinGW)

    */

    p = uri;

    while(*p == ' ') p++;

    for(q=uri;*p;p++) {if((*p == '\\' && p[1] == '\\')) {continue;} else {*q++ = *p;}}

    while((q - 1) >= uri && *(q - 1) == ' ') q--;

    *q = '\0';

    p = uri;

    /* break up the url into coarse pieces */

    if(*p == LBRACKET) {

        prefix = p;

        ret = collectprefixparams(p,&next); /* collect the prefix; convert to & form */

        if(ret != NC_NOERR)

            {THROW(NC_EURL);}

         p = next;

    } else {

  prefix = NULL;

    }

    tmp.uri = p; /* will be the core */

    /* Skip past the core of the url */

    next = nclocate(p,"?#");

    if(next != NULL) {

  int c = *next;

  terminate(next);

  next++;

  if(c == '?') {

      tmp.query = next;

      next = nclocate(next,"#");

      if(next == NULL)

    tmp.fragment = NULL;

      else {

    terminate(next);

    next++;

          tmp.fragment = next;

      }

  } else { /*c == '#'*/

      tmp.fragment = next;

  }

    }

    /* Parse the prefix parameters */

    if(prefix != NULL) {

        if(parselist(prefix,params) != NC_NOERR)

            {THROW(NC_EURL);}

    }

    /* Parse the fragment parameters into the params list */

    if(tmp.fragment != NULL) {

        if(parselist(tmp.fragment,params) != NC_NOERR)

            {THROW(NC_EURL);}

    }

    /* Remove duplicates */

    removedups(params);

    tmp.fraglist = params;

    params = NULL;

    /* Parse the query */

    if(tmp.query != NULL) {

        if(parselist(tmp.query,querylist) != NC_NOERR)

            {THROW(NC_EURL);}

  tmp.querylist = querylist;

  querylist = NULL;

    }

    /* Now parse the core of the url */

    p = tmp.uri;

    /* Mark the protocol */

    tmp.protocol = p;

    p = strchr(p,':');

    if(!p)

  {THROW(NC_EURL);}

    terminate(p); /*overwrite colon*/

    p++; /* skip the colon */

    if(strlen(tmp.protocol)==0)

  {THROW(NC_EURL);}

    /*

       The legal formats for file: urls are a problem since

       many variants are often accepted.

       By RFC, the proper general format is: file://host/path,

       where the 'host' can be omitted and defaults to 'localhost'.

       and the path includes the leading '/'.

       So, assuming no host, the format is: "file:///path".

       Some implementations, however, ignore the host, and allow

       the format: file:/path.

       We also simplify things by assuming the host part is always empty.

       which means we can have file:///path, but not file://..../path.

       Note also in all cases, the leading '/' is considered part of the path,

       which is then assumed to be an absolute path. But also note that

       the windows drive letter has to be taken into account. Our rule is that

       if the path looks like D:...,

       where D is a single alphabetic letter (a-z or A-Z),

       then it is a windows path and can be use in place of a /path.

       Note also that it is desirable to support relative paths even

       though the RFC technically does not allow this. This will occur

       if the form is file://path where path does not start with '/'.

       The rules implemented here (for file:) are then as follows

       1. file:D:... : assume D: is a windows drive letter and treat D:... as the path

       2. file:/X, where X does not start with a slash: treat /X as the path.

       3. file://D:... : assume D: is a windows drive letter and treat as the path

       4. file:///X, where X does not start with a slash: treat /X as the path.

       5. file://X, where X does not start with a slash: treat X as the

          relative path.

       All other cases are disallowed.

    */

    isfile = (strcmp(tmp.protocol,"file")==0);

    if(isfile) {

  size_t l = strlen(p); /* to test if we have enough characters */

  hashost = 0; /* always */

  if(l >= 2 && p[1] == ':' && strchr(DRIVELETTERS,p[0]) != NULL) { /* case 1 */

      ; /* p points to the start of the path */

        } else if(l >= 2 && p[0] == '/' && p[1] != '/') { /* case 2 */

      ; /* p points to the start of the path */

  } else if(l >= 4 && p[0] == '/' && p[1] == '/'

    && p[3] == ':' && strchr(DRIVELETTERS,p[2]) != NULL) { /* case 3 */

      p = p+2; /* points to the start of the windows path */

        } else if(l >= 4 && p[0] == '/' && p[1] == '/' && p[2] == '/' && p[3] != '/') { /* case 4 */

      p += 2; /* points to the start of the path */

        } else if(l >= 4 && p[0] == '/' && p[1] == '/' && p[2] != '/') { /* case 5 */

      p += 2; /* points to the start of the path */

        } else /* everything else is illegal */

      {THROW(NC_EURL);}

    } else {

        if(p[0] != '/' || p[1] != '/') /* must be proto:// */

      {THROW(NC_EURL);}

  p += 2;

        hashost = 1; /* Assume we have a hostname */

    }

    if(!hashost) {

        tmp.path = p;

  pathchar = EOFCHAR;

    } else { /* assume there should be a host section */

  /* We already extracted the query and/or fragment sections above,

           so locate the end of the host section and therefore the start

           of the path.

        */

  tmp.host = p;

        p  = nclocate(p,"/");

  if(p == NULL) { /* no path */

      tmp.path = NULL; /* default */

      pathchar = EOFCHAR;

  } else {

      tmp.path = p; /* save ptr to rest of the path */

      pathchar = *p; /* save leading char of the path */

      terminate(p); /* overwrite the leading char of the path; restored below */

  }

    }

    /* Nullify tmp.host for consistency */

    if(tmp.host != NULL && strlen(tmp.host)==0) {tmp.host = NULL;}

    if(tmp.host != NULL) {/* Parse the host section */

        char* pp;

  /* Check for leading user:pwd@ */

        char* newhost = strchr(tmp.host,'@');

        if(newhost != NULL) {

      if(newhost == tmp.host)

    {THROW(NC_EURL);} /* we have proto://@ */

      terminate(newhost); /* overwrite '@' */

      newhost++; /* should point past usr+pwd */

      tmp.user = tmp.host;

      /* Break user+pwd into two pieces */

      pp = strchr(tmp.user,':');

      if(pp == NULL)

    {THROW(NC_EURL);} /* we have user only */

      terminate(pp); /* overwrite ':' */

      pp++;

      if(strlen(tmp.user)==0)

    {THROW(NC_EURL);} /* we have empty user */

      if(strlen(pp)==0)

    {THROW(NC_EURL);} /* we have empty password */

      tmp.password = pp;

      tmp.host = newhost;

  }

  /* Breakup host into host + port */

  pp = tmp.host;

        pp = strchr(pp,':');

        if(pp != NULL) { /* there is a port */

      terminate(pp); /* overwrite ':' */

      pp++; /* skip colon */

      if(strlen(tmp.host) == 0)

    {THROW(NC_EURL);} /* empty host */

      if(strlen(pp)==0)

    {THROW(NC_EURL);} /* empty port */

      tmp.port = pp;

      /* The port must look something like a number */

      for(pp=tmp.port;*pp;pp++) {

          if(strchr("0123456789-",*pp) == NULL)

        {THROW(NC_EURL);}  /* probably not a real port, fail */

      }

  } /* else no port */

    }

    /* Fill in duri from tmp */

    duri = (NCURI*)calloc(1,sizeof(NCURI));

    if(duri == NULL)

      {THROW(NC_ENOMEM);}

    /* save original uri */

    duri->uri = strdup(uri0);

    duri->protocol = nulldup(tmp.protocol);

    /* before saving, we need to decode the user+pwd */

    duri->user = NULL;

    duri->password = NULL;

    if(tmp.user != NULL)

        duri->user = ncuridecode(tmp.user);

    if(tmp.password != NULL)

        duri->password = ncuridecode(tmp.password);

    duri->host = nulldup(tmp.host);

    duri->port = nulldup(tmp.port);

    if(tmp.path != NULL) {

  /* We need to add back the previously overwritten path lead char (if necessary);

           this must be done after all host section related pieces have been captured */

  if(pathchar != EOFCHAR)

      *tmp.path = pathchar;

        duri->path = nulldup(tmp.path);

    }

    duri->query = NULL; /* let ensurequery fix this */

    duri->fragment = NULL; /* let ensurefrag fix this */

    duri->fraglist = tmp.fraglist; tmp.fraglist = NULL;

    duri->querylist = tmp.querylist; tmp.querylist = NULL;

    /* make sure query and fragment strings are defined */

    ensurequerylist(duri);

    ensurefraglist(duri);

    if(durip)

      *durip = duri;

    else

      free(duri);

#ifdef NCXDEBUG

  {

        fprintf(stderr,"duri:");

  fprintf(stderr," protocol=|%s|",FIX(duri->protocol));

  fprintf(stderr," user=|%s|",FIX(duri->user));

  fprintf(stderr," password=|%s|",FIX(duri->password));

  fprintf(stderr," host=|%s|",FIX(duri->host));

  fprintf(stderr," port=|%s|",FIX(duri->port));

  fprintf(stderr," path=|%s|",FIX(duri->path));

  fprintf(stderr," query=|%s|",FIX(duri->query));

  fprintf(stderr," fragment=|%s|",FIX(duri->fragment));

        fprintf(stderr,"\n");

    }

#endif

done:

    if(uri != NULL)

      free(uri);

    freestringlist(params);

    freestringlist(querylist);

    if(tmp.fraglist)

      nclistfreeall(tmp.fraglist);

    if(tmp.querylist)

      nclistfreeall(tmp.querylist);

    return ret;

}

static void

freestringlist(NClist* list)

{

    if(list != NULL) {

  size_t i;

  for(i=0;i<nclistlength(list);i++) {

      void* p = nclistget(list,i);

      nullfree(p);

  }

        nclistfree(list);

    }

}

#if 0

static void

freestringvec(char** list)

{

    if(list != NULL) {

  char** p;

        for(p=list;*p;p++) {nullfree(*p);}

  nullfree(list);

    }

}

#endif

void

ncurifree(NCURI* duri)

{

    if(duri == NULL) return;

    nullfree(duri->uri);

    nullfree(duri->protocol);

    nullfree(duri->user);

    nullfree(duri->password);

    nullfree(duri->host);

    nullfree(duri->port);

    nullfree(duri->path);

    nullfree(duri->query);

    nullfree(duri->fragment);

    nclistfreeall(duri->querylist);

    nclistfreeall(duri->fraglist);

    free(duri);

}

/* Replace the protocol */

int

ncurisetprotocol(NCURI* duri,const char* protocol)

{

    nullfree(duri->protocol);

    duri->protocol = strdup(protocol);

    return (NC_NOERR);

}

/* Replace the host */

int

ncurisethost(NCURI* duri,const char* host)

{

    nullfree(duri->host);

    duri->host = strdup(host);

    return (NC_NOERR);

}

/* Replace the path */

int

ncurisetpath(NCURI* duri,const char* newpath)

{

    nullfree(duri->path);

    duri->path = strdup(newpath);

    return (NC_NOERR);

}

/* Replace the query */

int

ncurisetquery(NCURI* duri,const char* query)

{

    int ret = NC_NOERR;

    nclistfreeall((NClist*)duri->querylist);

    nullfree(duri->query);

    duri->query = NULL;

    duri->querylist = NULL;

    if(query != NULL && strlen(query) > 0) {

        duri->query = strdup(query);

  ensurequerylist(duri);

    }

    return ret;

}

/* Replace the fragments*/

int

ncurisetfragments(NCURI* duri,const char* fragments)

{

    int ret = NC_NOERR;

    nclistfreeall((NClist*)duri->fraglist);

    nullfree(duri->fragment);

    duri->fragment = NULL;

    duri->fraglist = NULL;

    if(fragments != NULL && strlen(fragments) > 0) {

  duri->fragment = strdup(fragments);

  ensurefraglist(duri);

    }

    return ret;

}

/* Replace the path */

int

ncurirebuild(NCURI* duri)

{

    char* surl = ncuribuild(duri,NULL,NULL,NCURIALL);

    nullfree(duri->uri);

    duri->uri = surl;

    return (NC_NOERR);

}

/* Replace a specific fragment key*/

int

ncurisetfragmentkey(NCURI* duri, const char* key, const char* value)

{

    int ret = NC_NOERR;

    int pos = -1;

    ensurefraglist(duri);

    pos = ncfind(duri->fraglist, key);

    if(pos < 0) { /* does not exist */

  if(duri->fraglist == NULL) duri->fraglist = nclistnew();

  nclistpush(duri->fraglist,strdup(key));

  nclistpush(duri->fraglist,strdup(value));

    } else {

        nullfree(nclistget(duri->fraglist,(size_t)pos+1));

        nclistset(duri->fraglist,(size_t)pos+1,strdup(value));

    }

    /* Rebuild the fragment */

    nullfree(duri->fragment); duri->fragment = NULL;

    if((ret = ensurefraglist(duri))) goto done;

done:

    return ret;

}

/* Replace or add a specific fragment key*/

int

ncuriappendfragmentkey(NCURI* duri,const char* key, const char* value)

{

    int ret = NC_NOERR;

    int pos = -1;

    ensurefraglist(duri);

    pos = ncfind(duri->fraglist, key);

    if(pos < 0) { /* does not exist */

  nclistpush((NClist*)duri->fraglist,strdup(key));

  nclistpush((NClist*)duri->fraglist,nulldup(value));

    } else {

        nullfree(nclistget(duri->fraglist,(size_t)pos+1));

  nclistset(duri->fraglist,(size_t)pos+1,nulldup(value));

    }

    /* Rebuild the fragment */

    nullfree(duri->fraglist); duri->fraglist = NULL;

    if((ret=ensurefraglist(duri))) goto done;

done:

    return ret;

}

/* Replace a specific query key*/

int

ncurisetquerykey(NCURI* duri,const char* key, const char* value)

{

    int ret = NC_NOERR;

    int pos = -1;

    ensurequerylist(duri);

    pos = ncfind(duri->querylist, key);

    if(pos < 0) { /* does not exist */

  if(duri->querylist == NULL) duri->querylist = nclistnew();

  nclistpush(duri->querylist,key);

  nclistpush(duri->querylist,value);

    } else {

        nullfree(nclistget(duri->querylist,(size_t)pos+1));

        nclistset(duri->querylist,(size_t)pos+1,strdup(value));

    }

    /* Rebuild the query */

    nullfree(duri->query); duri->query = NULL;

    if((ret = ensurequerylist(duri))) goto done;

done:

    return ret;

}

/* Replace or add a specific query key*/

int

ncuriappendquerykey(NCURI* duri,const char* key, const char* value)

{

    int ret = NC_NOERR;

    int pos = -1;

    ensurequerylist(duri);

    pos = ncfind(duri->querylist, key);

    if(pos < 0) { /* does not exist */

  nclistpush((NClist*)duri->querylist,strdup(key));

  nclistpush((NClist*)duri->querylist,nulldup(value));

    } else {

        nullfree(nclistget(duri->querylist,(size_t)pos+1));

  nclistset(duri->querylist,(size_t)pos+1,nulldup(value));

    }

    /* Rebuild the query */

    nullfree(duri->querylist); duri->querylist = NULL;

    if((ret=ensurequerylist(duri))) goto done;

done:

    return ret;

}

#if 0

/* Replace the constraints */

int

ncurisetconstraints(NCURI* duri,const char* constraints)

{

    char* proj = NULL;

    char* select = NULL;

    const char* p;

    if(duri->constraint != NULL) free(duri->constraint);

    if(duri->projection != NULL) free(duri->projection);

    if(duri->selection != NULL) free(duri->selection);

    duri->constraint = NULL;

    duri->projection = NULL;

    duri->selection = NULL;

    if(constraints == NULL || strlen(constraints)==0) return (NC_ECONSTRAINTS);

    duri->constraint = nulldup(constraints);

    if(*duri->constraint == '?')

  nclshift1(duri->constraint);

    p = duri->constraint;

    proj = (char*) p;

    select = strchr(proj,'&');

    if(select != NULL) {

        size_t plen = (size_t)(select - proj);

  if(plen == 0) {

      proj = NULL;

  } else {

      proj = (char*)malloc(plen+1);

      memcpy((void*)proj,p,plen);

      proj[plen] = EOFCHAR;

  }

  select = nulldup(select);

    } else {

  proj = nulldup(proj);

  select = NULL;

    }

    duri->projection = proj;

    duri->selection = select;

    return NC_NOERR;

}

#endif

/* Construct a complete NC URI.

   Optionally with the constraints.

   Optionally with the user parameters.

   Caller frees returned string.

   Optionally encode the pieces.

*/

char*

ncuribuild(NCURI* duri, const char* prefix, const char* suffix, int flags)

{

    char* newuri = NULL;

    NCbytes* buf = ncbytesnew();

    const int encodepath = (flags&NCURIENCODEPATH ? 1 : 0);

    const int encodequery = (flags&NCURIENCODEQUERY ? 1 : 0);

    if(prefix != NULL)

  ncbytescat(buf,prefix);

    ncbytescat(buf,duri->protocol);

    ncbytescat(buf,"://"); /* this will produce file:///... */

    if((flags & NCURIPWD) && duri->user != NULL && duri->password != NULL) {

  /* The user and password must be encoded */

        char* encoded = ncuriencodeonly(duri->user,userpwdallow);

  ncbytescat(buf,encoded);

  nullfree(encoded);

  ncbytescat(buf,":");

  encoded = ncuriencodeonly(duri->password,userpwdallow);

  ncbytescat(buf,encoded);

  nullfree(encoded);

  ncbytescat(buf,"@");

    }

    if(duri->host != NULL) ncbytescat(buf,duri->host);

    if(duri->port != NULL) {

  ncbytescat(buf,":");

  ncbytescat(buf,duri->port);

    }

    if((flags & NCURIPATH)) {

  if(duri->path == NULL)

      ncbytescat(buf,"/");

  else if(encodepath) {

      char* encoded = ncuriencodeonly(duri->path,pathallow);

      ncbytescat(buf,encoded);

      nullfree(encoded);

  } else

      ncbytescat(buf,duri->path);

    }

    /* The suffix is intended to some kind of path extension (e.g. .dds)

       so insert here

    */

    if(suffix != NULL)

  ncbytescat(buf,suffix);

    /* The query and the querylist are assumed to be unencoded */

    if(flags & NCURIQUERY) {

  ensurequerylist(duri);

        if(duri->query != NULL) {

            ncbytescat(buf,"?");

      if(encodequery) {

          char* encoded = ncuriencodeonly(duri->query,queryallow);

          ncbytescat(buf,encoded);

          nullfree(encoded);

      } else

          ncbytescat(buf,duri->query);

  }

    }

    if(flags & NCURIFRAG) {

  ensurefraglist(duri);

        if(duri->fragment != NULL) {

            ncbytescat(buf,"#");

      ncbytescat(buf,duri->fragment);

  }

    }

    ncbytesnull(buf);

    newuri = ncbytesextract(buf);

    ncbytesfree(buf);

    return newuri;

}

const char*

ncurifragmentlookup(NCURI* uri, const char* key)

{

  int i;

  char* value = NULL;

  if(uri == NULL || key == NULL) return NULL;

  if(ensurefraglist(uri)) return NULL;

  i = ncfind(uri->fraglist,key);

  if(i < 0) return NULL;

  value = nclistget(uri->fraglist,(size_t)i+1);

  return value;

}

const char*

ncuriquerylookup(NCURI* uri, const char* key)

{

  int i;

  char* value = NULL;

  if(uri == NULL || key == NULL) return NULL;

  if(ensurequerylist(uri)) return NULL;

  i = ncfind(uri->querylist,key);

  if(i < 0) return NULL;

  value = nclistget(uri->querylist,(size_t)i+1);

  return value;

}

#if 0

/* Obtain the complete list of fragment pairs in envv format */

const char**

ncurifragmentparams(NCURI* uri)

{

    ensurefraglist(uri);

    return (const char**)nclistcontents(uri->fraglist;

}

/* Obtain the complete list of query pairs in envv format */

const char**

ncuriqueryparams(NCURI* uri)

{

    ensurequerylist(uri);

    return (const char**)uri->querylist;

}

int

ncuriremoveparam(NCURI* uri, const char* key)

{

    char** p;

    char** q = NULL;

    if(uri->fraglist == NULL) return NC_NOERR;

    for(q=uri->fraglist,p=uri->fraglist;*p;) {

        if(strcmp(key,*p)==0) {

      p += 2; /* skip this entry */

  } else {

      *q++ = *p++; /* move key */

      *q++ = *p++; /* move value */

  }

    }

    return NC_NOERR;

}

#endif

/* Internal version of lookup; returns the paired index of the key;

   case insensitive

 */

static int

ncfind(NClist* params, const char* key)

{

    size_t i;

    if(key == NULL) return -1;

    if(params == NULL) return -1;

    for(i=0;i<nclistlength(params);i+=2) {

        char* p=nclistget(params,(size_t)i);

  if(strcasecmp(key,p)==0) return i;

    }

    return -1;

}

#if 0

static void

ncparamfree(char** params)

{

    char** p;

    if(params == NULL) return;

    for(p=params;*p;p+=2) {

  free(*p);

  if(p[1] != NULL) free(p[1]);

    }

    free(params);

}

#endif

/* Return the ptr to the first occurrence of

   any char in the list. Return NULL if no

   occurrences

*/

static char*

nclocate(char* p, const char* charlist)

{

    for(;*p;p++) {

  if(*p == '\\') p++;

  else if(strchr(charlist,*p) != NULL)

      return p;

    }

    return NULL;

}

#if 0

/* Shift every char starting at p 1 place to the left */

static void

nclshift1(char* p)

{

    if(p != NULL && *p != EOFCHAR) {

  char* q = p++;

  while((*q++=*p++));

    }

}

/* Shift every char starting at p 1 place to the right */

static void

ncrshift1(char* p)

{

    char cur;

    cur = 0;

    do {

  char next = *p;

  *p++ = cur;

  cur = next;

    } while(cur != 0);

    *p = 0; /* make sure we are still null terminated */

}

#endif

/* Provide % encoders and decoders */

static const char* hexchars = "0123456789abcdefABCDEF";

static void

toHex(char b, char hex[2])

{

    hex[0] = hexchars[(b >> 4) & 0xf];

    hex[1] = hexchars[(b) & 0xf];

}

static int

fromHex(int c)

{

    if(c >= '0' && c <= '9') return (int) (c - '0');

    if(c >= 'a' && c <= 'f') return (int) (10 + (c - 'a'));

    if(c >= 'A' && c <= 'F') return (int) (10 + (c - 'A'));

    return 0;

}

/*

Support encode of user and password fields

*/

char*

ncuriencodeuserpwd(const char* s)

{

    return ncuriencodeonly(s,userpwdallow);

}

/* Return a string representing encoding of input; caller must free;

   watch out: will encode whole string, so watch what you give it.

   Allowable argument specifies characters that do not need escaping.

 */

char*

ncuriencodeonly(const char* s, const char* allowable)

{

    size_t slen;

    char* encoded;