X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FFormat.h;h=7601ae528aa7417dea1f8aa244d92452ee4b2315;hb=3cdd3857fbfacd9312a23214f54a47f156726927;hp=a270b43b36e0a6c6f961afc4984336c84de62659;hpb=afa85fd054e5e8c0297c440acb6be6a40f30fb86;p=folly.git

diff --git a/folly/Format.h b/folly/Format.h
index a270b43b..7601ae52 100644
--- a/folly/Format.h
+++ b/folly/Format.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,28 +14,18 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_FORMAT_H_
+#pragma once
 #define FOLLY_FORMAT_H_
 
-#include <array>
 #include <cstdio>
 #include <tuple>
 #include <type_traits>
-#include <vector>
-#include <deque>
-#include <map>
-#include <unordered_map>
-
-#include <double-conversion.h>
-
-#include "folly/FBVector.h"
-#include "folly/Conv.h"
-#include "folly/Range.h"
-#include "folly/Traits.h"
-#include "folly/Likely.h"
-#include "folly/String.h"
-#include "folly/small_vector.h"
-#include "folly/FormatArg.h"
+
+#include <folly/Conv.h>
+#include <folly/Range.h>
+#include <folly/Traits.h>
+#include <folly/String.h>
+#include <folly/FormatArg.h>
 
 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
 #pragma GCC diagnostic push
@@ -51,6 +41,11 @@ template <class C>
 Formatter<true, C> vformat(StringPiece fmt, C&& container);
 template <class T, class Enable=void> class FormatValue;
 
+// meta-attribute to identify formatters in this sea of template weirdness
+namespace detail {
+class FormatterTag {};
+};
+
 /**
  * Formatter class.
  *
@@ -59,22 +54,13 @@ template <class T, class Enable=void> class FormatValue;
  * this directly, you have to use format(...) below.
  */
 
-template <bool containerMode, class... Args>
-class Formatter {
+/* BaseFormatter class. Currently, the only behavior that can be
+ * overridden is the actual formatting of positional parameters in
+ * `doFormatArg`. The Formatter class provides the default implementation.
+ */
+template <class Derived, bool containerMode, class... Args>
+class BaseFormatter {
  public:
-  /*
-   * Change whether or not Formatter should crash or throw exceptions if the
-   * format string is invalid.
-   *
-   * Crashing is desirable for literal format strings that are fixed at compile
-   * time.  Errors in the format string are generally programmer bugs, and
-   * should be caught early on in development.  Crashing helps ensure these
-   * problems are noticed.
-   */
-  void setCrashOnError(bool crash) {
-    crashOnError_ = crash;
-  }
-
   /**
    * Append to output.  out(StringPiece sp) may be called (more than once)
    */
@@ -109,32 +95,20 @@ class Formatter {
     return s;
   }
 
- private:
-  explicit Formatter(StringPiece str, Args&&... args);
-
-  // Not copyable
-  Formatter(const Formatter&) = delete;
-  Formatter& operator=(const Formatter&) = delete;
-
-  // Movable, but the move constructor and assignment operator are private,
-  // for the exclusive use of format() (below).  This way, you can't create
-  // a Formatter object, but can handle references to it (for streaming,
-  // conversion to string, etc) -- which is good, as Formatter objects are
-  // dangerous (they hold references, possibly to temporaries)
-  Formatter(Formatter&&) = default;
-  Formatter& operator=(Formatter&&) = default;
+  /**
+   * metadata to identify generated children of BaseFormatter
+   */
+  typedef detail::FormatterTag IsFormatter;
+  typedef BaseFormatter BaseType;
 
+ private:
   typedef std::tuple<FormatValue<
       typename std::decay<Args>::type>...> ValueTuple;
   static constexpr size_t valueCount = std::tuple_size<ValueTuple>::value;
 
-  void handleFormatStrError() const FOLLY_NORETURN;
-  template <class Output>
-  void appendOutput(Output& out) const;
-
   template <size_t K, class Callback>
   typename std::enable_if<K == valueCount>::type
-  doFormatFrom(size_t i, FormatArg& arg, Callback& cb) const {
+  doFormatFrom(size_t i, FormatArg& arg, Callback& /*cb*/) const {
     arg.error("argument index out of range, max=", i);
   }
 
@@ -142,7 +116,7 @@ class Formatter {
   typename std::enable_if<(K < valueCount)>::type
   doFormatFrom(size_t i, FormatArg& arg, Callback& cb) const {
     if (i == K) {
-      std::get<K>(values_).format(arg, cb);
+      static_cast<const Derived*>(this)->template doFormatArg<K>(arg, cb);
     } else {
       doFormatFrom<K+1>(i, arg, cb);
     }
@@ -153,18 +127,82 @@ class Formatter {
     return doFormatFrom<0>(i, arg, cb);
   }
 
+  template <size_t K>
+  typename std::enable_if<K == valueCount, int>::type
+  getSizeArgFrom(size_t i, const FormatArg& arg) const {
+    arg.error("argument index out of range, max=", i);
+  }
+
+  template <class T>
+  typename std::enable_if<std::is_integral<T>::value &&
+                          !std::is_same<T, bool>::value, int>::type
+  getValue(const FormatValue<T>& format, const FormatArg&) const {
+    return static_cast<int>(format.getValue());
+  }
+
+  template <class T>
+  typename std::enable_if<!std::is_integral<T>::value ||
+                          std::is_same<T, bool>::value, int>::type
+  getValue(const FormatValue<T>&, const FormatArg& arg) const {
+    arg.error("dynamic field width argument must be integral");
+  }
+
+  template <size_t K>
+  typename std::enable_if<K < valueCount, int>::type
+  getSizeArgFrom(size_t i, const FormatArg& arg) const {
+    if (i == K) {
+      return getValue(std::get<K>(values_), arg);
+    }
+    return getSizeArgFrom<K+1>(i, arg);
+  }
+
+  int getSizeArg(size_t i, const FormatArg& arg) const {
+    return getSizeArgFrom<0>(i, arg);
+  }
+
   StringPiece str_;
+
+ protected:
+  explicit BaseFormatter(StringPiece str, Args&&... args);
+
+  // Not copyable
+  BaseFormatter(const BaseFormatter&) = delete;
+  BaseFormatter& operator=(const BaseFormatter&) = delete;
+
+  // Movable, but the move constructor and assignment operator are private,
+  // for the exclusive use of format() (below).  This way, you can't create
+  // a Formatter object, but can handle references to it (for streaming,
+  // conversion to string, etc) -- which is good, as Formatter objects are
+  // dangerous (they hold references, possibly to temporaries)
+  BaseFormatter(BaseFormatter&&) = default;
+  BaseFormatter& operator=(BaseFormatter&&) = default;
+
   ValueTuple values_;
-  bool crashOnError_{true};
+};
+
+template <bool containerMode, class... Args>
+class Formatter : public BaseFormatter<Formatter<containerMode, Args...>,
+                                       containerMode,
+                                       Args...> {
+ private:
+  explicit Formatter(StringPiece& str, Args&&... args)
+      : BaseFormatter<Formatter<containerMode, Args...>,
+                      containerMode,
+                      Args...>(str, std::forward<Args>(args)...) {}
+
+  template <size_t K, class Callback>
+  void doFormatArg(FormatArg& arg, Callback& cb) const {
+    std::get<K>(this->values_).format(arg, cb);
+  }
+
+  friend class BaseFormatter<Formatter<containerMode, Args...>,
+                             containerMode,
+                             Args...>;
 
   template <class... A>
   friend Formatter<false, A...> format(StringPiece fmt, A&&... arg);
-  template <class... A>
-  friend Formatter<false, A...> formatChecked(StringPiece fmt, A&&... arg);
   template <class C>
   friend Formatter<true, C> vformat(StringPiece fmt, C&& container);
-  template <class C>
-  friend Formatter<true, C> vformatChecked(StringPiece fmt, C&& container);
 };
 
 /**
@@ -173,7 +211,9 @@ class Formatter {
 template<bool containerMode, class... Args>
 std::ostream& operator<<(std::ostream& out,
                          const Formatter<containerMode, Args...>& formatter) {
-  auto writer = [&out] (StringPiece sp) { out.write(sp.data(), sp.size()); };
+  auto writer = [&out](StringPiece sp) {
+    out.write(sp.data(), std::streamsize(sp.size()));
+  };
   formatter(writer);
   return out;
 }
@@ -181,8 +221,9 @@ std::ostream& operator<<(std::ostream& out,
 /**
  * Formatter objects can be written to stdio FILEs.
  */
-template<bool containerMode, class... Args>
-void writeTo(FILE* fp, const Formatter<containerMode, Args...>& formatter);
+template <class Derived, bool containerMode, class... Args>
+void writeTo(FILE* fp,
+             const BaseFormatter<Derived, containerMode, Args...>& formatter);
 
 /**
  * Create a formatter object.
@@ -190,16 +231,6 @@ void writeTo(FILE* fp, const Formatter<containerMode, Args...>& formatter);
  * std::string formatted = format("{} {}", 23, 42).str();
  * LOG(INFO) << format("{} {}", 23, 42);
  * writeTo(stdout, format("{} {}", 23, 42));
- *
- * Note that format() will crash the program if the format string is invalid.
- * Normally, the format string is a fixed string literal specified by the
- * programmer.  Invalid format strings are normally programmer bugs, and should
- * be caught early on during development.  Crashing helps ensure these bugs are
- * found.
- *
- * Use formatChecked() if you have a dynamic format string (for example, a user
- * supplied value).  formatChecked() will throw an exception rather than
- * crashing the program.
  */
 template <class... Args>
 Formatter<false, Args...> format(StringPiece fmt, Args&&... args) {
@@ -208,18 +239,12 @@ Formatter<false, Args...> format(StringPiece fmt, Args&&... args) {
 }
 
 /**
- * Create a formatter object from a dynamic format string.
- *
- * This is identical to format(), but throws an exception if the format string
- * is invalid, rather than aborting the program.  This allows it to be used
- * with user-specified format strings which are not guaranteed to be well
- * formed.
+ * Like format(), but immediately returns the formatted string instead of an
+ * intermediate format object.
  */
 template <class... Args>
-Formatter<false, Args...> formatChecked(StringPiece fmt, Args&&... args) {
-  Formatter<false, Args...> f(fmt, std::forward<Args>(args)...);
-  f.setCrashOnError(false);
-  return f;
+inline std::string sformat(StringPiece fmt, Args&&... args) {
+  return format(fmt, std::forward<Args>(args)...).str();
 }
 
 /**
@@ -242,19 +267,37 @@ Formatter<true, Container> vformat(StringPiece fmt, Container&& container) {
 }
 
 /**
- * Create a formatter object from a dynamic format string.
- *
- * This is identical to vformat(), but throws an exception if the format string
- * is invalid, rather than aborting the program.  This allows it to be used
- * with user-specified format strings which are not guaranteed to be well
- * formed.
+ * Like vformat(), but immediately returns the formatted string instead of an
+ * intermediate format object.
  */
 template <class Container>
-Formatter<true, Container> vformatChecked(StringPiece fmt,
-                                          Container&& container) {
-  Formatter<true, Container> f(fmt, std::forward<Container>(container));
-  f.setCrashOnError(false);
-  return f;
+inline std::string svformat(StringPiece fmt, Container&& container) {
+  return vformat(fmt, std::forward<Container>(container)).str();
+}
+
+/**
+ * Wrap a sequence or associative container so that out-of-range lookups
+ * return a default value rather than throwing an exception.
+ *
+ * Usage:
+ * format("[no_such_key"], defaulted(map, 42))  -> 42
+ */
+namespace detail {
+template <class Container, class Value> struct DefaultValueWrapper {
+  DefaultValueWrapper(const Container& container, const Value& defaultValue)
+    : container(container),
+      defaultValue(defaultValue) {
+  }
+
+  const Container& container;
+  const Value& defaultValue;
+};
+}  // namespace
+
+template <class Container, class Value>
+detail::DefaultValueWrapper<Container, Value>
+defaulted(const Container& c, const Value& v) {
+  return detail::DefaultValueWrapper<Container, Value>(c, v);
 }
 
 /**
@@ -311,10 +354,14 @@ void formatNumber(StringPiece val, int prefixLen, FormatArg& arg,
  * formatString(fmt.str(), arg, cb); but avoids creating a temporary
  * string if possible.
  */
-template <class FormatCallback, bool containerMode, class... Args>
-void formatFormatter(const Formatter<containerMode, Args...>& formatter,
-                     FormatArg& arg,
-                     FormatCallback& cb);
+template <class FormatCallback,
+          class Derived,
+          bool containerMode,
+          class... Args>
+void formatFormatter(
+    const BaseFormatter<Derived, containerMode, Args...>& formatter,
+    FormatArg& arg,
+    FormatCallback& cb);
 
 }  // namespace format_value
 
@@ -340,10 +387,51 @@ void formatFormatter(const Formatter<containerMode, Args...>& formatter,
  * empty string)
  */
 
+namespace detail {
+
+template <class T, class Enable = void>
+struct IsFormatter : public std::false_type {};
+
+template <class T>
+struct IsFormatter<
+    T,
+    typename std::enable_if<
+        std::is_same<typename T::IsFormatter, detail::FormatterTag>::value>::
+        type> : public std::true_type {};
+} // folly::detail
+
+// Deprecated API. formatChecked() et. al. now behave identically to their
+// non-Checked counterparts.
+template <class... Args>
+Formatter<false, Args...> formatChecked(StringPiece fmt, Args&&... args) {
+  return format(fmt, std::forward<Args>(args)...);
+}
+template <class... Args>
+inline std::string sformatChecked(StringPiece fmt, Args&&... args) {
+  return formatChecked(fmt, std::forward<Args>(args)...).str();
+}
+template <class Container>
+Formatter<true, Container> vformatChecked(StringPiece fmt,
+                                          Container&& container) {
+  return vformat(fmt, std::forward<Container>(container));
+}
+template <class Container>
+inline std::string svformatChecked(StringPiece fmt, Container&& container) {
+  return vformatChecked(fmt, std::forward<Container>(container)).str();
+}
+template <class Str, class... Args>
+typename std::enable_if<IsSomeString<Str>::value>::type
+formatChecked(Str* out, StringPiece fmt, Args&&... args) {
+  formatChecked(fmt, std::forward<Args>(args)...).appendTo(*out);
+}
+template <class Str, class Container>
+typename std::enable_if<IsSomeString<Str>::value>::type
+vformatChecked(Str* out, StringPiece fmt, Container&& container) {
+  vformatChecked(fmt, std::forward<Container>(container)).appendTo(*out);
+}
+
 }  // namespace folly
 
-#include "folly/Format-inl.h"
+#include <folly/Format-inl.h>
 
 #pragma GCC diagnostic pop
-
-#endif /* FOLLY_FORMAT_H_ */