SafeCStringIO.cpp

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#include "blocxx/BLOCXX_config.h"
#include "blocxx/SafeCStringIO.hpp"
#include "blocxx/SafeCString.hpp"
  /* to get OverflowException and RESULT_TRUNCATED */
#include "blocxx/String.hpp"
#include "blocxx/StringBuffer.hpp"
#include "blocxx/IOException.hpp"
#include <cstdio>

namespace BLOCXX_NAMESPACE
{
namespace SafeCString
{

char * fgets_trunc(char * dst, std::size_t dstsize, FILE * fp)
{
   char * res = std::fgets(dst, dstsize, fp);
   if (!res)
   {
      if (feof(fp))
      {
         return 0;
      }
      BLOCXX_THROW(blocxx::IOException, "read error");
   }
   return res;
}

char * fgets_check(char * dst, std::size_t dstsize, FILE * fp)
{
   std::size_t const end = dstsize - 1;
   char savechar = dst[end];
   dst[end] = ' '; // anything but '\0'
   char * res = std::fgets(dst, dstsize, fp);
   char endchar = dst[end];
   dst[end] = savechar;
   if (res)
   {
      if (endchar == '\0' && (end == 0 || dst[end - 1] != '\n'))
      {
         // No newline at end.  Either the input line was truncated, or
         // we read the last line of the file and it had no newline.
         // We test for EOF to distinguish the two cases.  Since the EOF
         // marker doesn't get set until we actually try to read past EOF,
         // we first peek one character ahead.
         std::ungetc(std::fgetc(fp), fp);
         if (!feof(fp))
         {
            BLOCXX_THROW_ERR(
               OverflowException, "fgets overflow", RESULT_TRUNCATED);
         }
      }
      return res;
   }
   else
   {
      if (feof(fp))
      {
         return 0;
      }
      BLOCXX_THROW(blocxx::IOException, "read error");
   }
}

String fget_string(FILE * fp, std::size_t const max_chars)
{
   // This could perhaps be made more efficient by reading directly into a
   // custom resizable character array.
   std::size_t const BUFSIZE = 8 * 1024;
   StringBuffer sb;
   char buf[BUFSIZE];
   while (!sb.endsWith('\n') && sb.length() <= max_chars &&
      fgets_trunc(buf, fp))
   {
      sb.append(buf);
   }
   if (sb.length() > max_chars)
   {
      BLOCXX_THROW(StringConversionException, "input line too long");
   }
   return sb.releaseString();
}

} // namespace SafeCString
} // namespace BLOCXX_NAMESPACE