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utils.h
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utils.h
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#pragma once
#include <array>
#include <cpp11/R.hpp>
#include <cstring>
#include <sstream>
#include <string>
namespace vroom {
inline bool
is_comment(const char* begin, const char* end, const std::string& comment) {
if (comment.empty() || comment.size() >= static_cast<size_t>(end - begin)) {
return false;
}
return strncmp(comment.data(), begin, comment.size()) == 0;
}
template <typename T>
inline size_t skip_rest_of_line(const T& source, size_t start) {
auto out = memchr(source.data() + start, '\n', source.size() - start);
if (!out) {
return (source.size());
}
return static_cast<const char*>(out) - source.data();
}
inline bool
is_empty_line(const char* begin, const char* end, const bool skip_empty_rows) {
if (!skip_empty_rows) {
return false;
}
if (skip_empty_rows && *begin == '\n') {
return true;
}
while (begin < end && (*begin == ' ' || *begin == '\t' || *begin == '\r')) {
++begin;
}
return *begin == '\n';
}
inline bool is_blank_or_comment_line(
const char* begin,
const char* end,
const std::string& comment,
const bool skip_empty_rows) {
if (!skip_empty_rows && comment.empty()) {
return false;
}
if (skip_empty_rows && (*begin == '\n' || *begin == '\r')) {
return true;
}
while (begin < end && (*begin == ' ' || *begin == '\t')) {
++begin;
}
if ((skip_empty_rows && (*begin == '\n' || *begin == '\r')) ||
(!comment.empty() &&
strncmp(begin, comment.data(), comment.size()) == 0)) {
return true;
}
return false;
}
inline bool is_crlf(const char* buf, size_t pos, size_t end) {
return buf[pos] == '\r' && pos + 1 < end && buf[pos + 1] == '\n';
}
enum newline_type {
CR /* linux */,
CRLF /* windows */,
LF /* old macOS */,
NA /* unknown */
};
template <typename T>
static std::pair<size_t, newline_type>
find_next_non_quoted_newline(const T& source, size_t start, const char quote) {
if (start > source.size() - 1) {
return {source.size() - 1, NA};
}
std::array<char, 4> query = {'\r', '\n', quote, '\0'};
auto buf = source.data();
size_t pos = start;
size_t end = source.size() - 1;
bool in_quote = false;
while (pos < end) {
size_t buf_offset = strcspn(buf + pos, query.data());
pos = pos + buf_offset;
auto c = buf[pos];
if (c == '\n' || c == '\r') {
if (in_quote) {
++pos;
continue;
}
if (c == '\n') {
return {pos, LF};
}
if (is_crlf(buf, pos, end)) {
return {pos + 1, CRLF};
}
return {pos, CR};
}
else if (c == quote) {
in_quote = !in_quote;
}
++pos;
}
if (pos > end) {
return {end, NA};
}
return {pos, NA};
}
template <typename T>
static std::pair<size_t, newline_type> find_next_newline(
const T& source,
size_t start,
const std::string& comment,
const bool skip_empty_rows,
bool embedded_nl,
const char quote) {
if (start >= source.size()) {
return {source.size() - 1, NA};
}
if (embedded_nl) {
size_t value;
newline_type nl;
std::tie(value, nl) = find_next_non_quoted_newline(source, start, quote);
// REprintf("%i\n", value);
return {value, nl};
}
const char* begin = source.data() + start;
const char* end = source.data() + source.size();
std::array<char, 3> query = {'\r', '\n', '\0'};
while (begin && begin < end) {
size_t offset = strcspn(begin, query.data());
// REprintf("%i\n", offset);
begin += offset;
break;
if (!(begin && begin + 1 < end &&
is_blank_or_comment_line(begin + 1, end, comment, skip_empty_rows))) {
break;
}
}
if (!begin) {
return {source.size() - 1, NA};
}
size_t pos = begin - source.data();
if (begin[0] == '\n') {
return {pos, LF};
}
if (begin[0] == '\r') {
if (is_crlf(source.data(), pos, end - source.data())) {
return {pos + 1, CRLF};
}
return {pos, CR};
}
return {pos, NA};
}
template <typename T> T get_env(const char* name, T default_value) {
char* p;
p = getenv(name);
if (!p || strlen(p) == 0) {
return default_value;
}
std::stringstream ss(p);
double out;
ss >> out;
return out;
}
inline bool is_space(const char* c) {
return *c == ' ' || *c == '\t' || *c == '\0' || *c == '\r';
}
inline void trim_whitespace(const char*& begin, const char*& end) {
while (begin != end && is_space(begin)) {
++begin;
}
while (end != begin && is_space(end - 1)) {
--end;
}
}
template <typename T> size_t skip_bom(const T& source) {
/* Skip Unicode Byte Order Marks
https://en.wikipedia.org/wiki/Byte_order_mark#Representations_of_byte_order_marks_by_encoding
00 00 FE FF: UTF-32BE
FF FE 00 00: UTF-32LE
FE FF: UTF-16BE
FF FE: UTF-16LE
EF BB BF: UTF-8
*/
auto size = source.size();
auto begin = source.data();
switch (begin[0]) {
// UTF-32BE
case '\x00':
if (size >= 4 && begin[1] == '\x00' && begin[2] == '\xFE' &&
begin[3] == '\xFF') {
return 4;
}
break;
// UTF-8
case '\xEF':
if (size >= 3 && begin[1] == '\xBB' && begin[2] == '\xBF') {
return 3;
}
break;
// UTF-16BE
case '\xfe':
if (size >= 2 && begin[1] == '\xff') {
return 2;
}
break;
case '\xff':
if (size >= 2 && begin[1] == '\xfe') {
// UTF-32 LE
if (size >= 4 && begin[2] == '\x00' && begin[3] == '\x00') {
return 4;
} else {
// UTF-16 LE
return 2;
}
}
break;
}
return 0;
}
// This skips leading blank lines and comments (if needed)
template <typename T>
size_t find_first_line(
const T& source,
size_t skip,
const char* comment,
const bool skip_empty_rows,
const bool embedded_nl,
const char quote) {
auto begin = skip_bom(source);
/* Skip skip parameters, comments and blank lines */
while (bool should_skip =
(begin < source.size() - 1 && is_blank_or_comment_line(
source.data() + begin,
source.data() + source.size(),
comment,
skip_empty_rows)) ||
skip > 0) {
std::tie(begin, std::ignore) = find_next_newline(
source,
begin,
"",
/* skip_empty_rows */ false,
embedded_nl,
quote);
++begin;
skip = skip > 0 ? skip - 1 : skip;
}
return begin;
}
inline bool
matches(const char* start, const char* end, const std::string& needle) {
if (end <= start || needle.empty() ||
static_cast<unsigned long>(end - start) < needle.size()) {
return false;
}
bool res = strncmp(start, needle.data(), needle.size()) == 0;
return res;
}
inline bool has_expected_line_ending(newline_type nl, const char value) {
if (nl == CR && value == '\r') {
return true;
}
return value == '\n';
}
} // namespace vroom