format.C

#include "random.h"
#include <cstdio>
#include <cstdlib>
#include <cstring>

/*
    GenRan: non-Gaussian random field generator.
    Copyright (C) 2006 Peter Grassl
    Distributed under the MIT licence.

    Minimal reader for .ini-style input files: keys on the left, ':' or '='
    separator, value on the right. Each lookup reopens and rescans the
    file; this is O(K·filesize) for K lookups but acceptable since a typical
    input has a dozen keys and a typical run reads them all once.
*/

namespace {

// Scan `fname` for a line whose start (case-insensitive) matches `lhs` and
// copy it into `out`. Returns true on hit; on miss leaves `out` empty.
bool readMatchingLine(const char *fname, const char *lhs, char *out, size_t out_size)
{
  FILE *inp = std::fopen(fname, "r");
  if (!inp) return false;
  out[0] = '\0';
  char buf[256];
  const size_t lhs_len = std::strlen(lhs);
  bool found = false;
  while (std::fgets(buf, sizeof(buf), inp)) {
    if (!strncasecmp(lhs, buf, lhs_len)) {
      std::strncpy(out, buf, out_size - 1);
      out[out_size - 1] = '\0';
      found = true;
      break;
    }
  }
  std::fclose(inp);
  return found;
}

// Locate the value separator (`:` or `=`) in `line`. Returns NULL if none.
const char *valuePointer(const char *line)
{
  const char *ptr = std::strstr(line, ":");
  if (!ptr) ptr = std::strstr(line, "=");
  return ptr;
}

}  // namespace

int getint_ini(const char *fname, const char *lhs)
{
  char line[256];
  if (!readMatchingLine(fname, lhs, line, sizeof(line))) {
    // Distinguish "file missing" from "key missing" for the user.
    FILE *probe = std::fopen(fname, "r");
    if (!probe) {
      std::printf("File not found: '%s'\n", fname);
    } else {
      std::fclose(probe);
      std::printf("Cannot find string '%s' in ini file '%s'.\n", lhs, fname);
    }
    std::exit(-1);
  }
  const char *ptr = valuePointer(line);
  if (!ptr) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  int result;
  if (std::sscanf(ptr + 1, "%d", &result) != 1) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  return result;
}

double getdouble_ini(const char *fname, const char *lhs)
{
  char line[256];
  if (!readMatchingLine(fname, lhs, line, sizeof(line))) {
    FILE *probe = std::fopen(fname, "r");
    if (!probe) {
      std::printf("Ini file not found: '%s'\n", fname);
    } else {
      std::fclose(probe);
      std::printf("Cannot find string '%s' in ini file '%s'.\n", lhs, fname);
    }
    std::exit(-1);
  }
  const char *ptr = valuePointer(line);
  if (!ptr) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  double result;
  if (std::sscanf(ptr + 1, "%lf", &result) != 1) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  return result;
}

// Like getint_ini but returns false (without exiting) when the key is
// missing. Still exits on a malformed line. The file must exist.
bool tryGetint_ini(const char *fname, const char *lhs, int *out)
{
  char line[256];
  if (!readMatchingLine(fname, lhs, line, sizeof(line))) {
    return false;
  }
  const char *ptr = valuePointer(line);
  if (!ptr) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  if (std::sscanf(ptr + 1, "%d", out) != 1) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  return true;
}

// Companion to getdouble_ini that returns false when the key is missing.
bool tryGetdouble_ini(const char *fname, const char *lhs, double *out)
{
  char line[256];
  if (!readMatchingLine(fname, lhs, line, sizeof(line))) {
    return false;
  }
  const char *ptr = valuePointer(line);
  if (!ptr) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  if (std::sscanf(ptr + 1, "%lf", out) != 1) {
    std::printf("Cannot parse line '%s' in ini file '%s'\n", lhs, fname);
    std::exit(-1);
  }
  return true;
}