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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Apache License, Version 2.0. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Apache License, Version 2.0, please send an email to
* [email protected]. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Apache License, Version 2.0.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;
using Microsoft.Scripting;
using Microsoft.Scripting.Runtime;
using Microsoft.Scripting.Utils;
using IronPython.Modules;
using IronPython.Runtime.Operations;
namespace IronPython.Runtime {
/// <summary>
/// New string formatter for 'str'.format(...) calls and support for the Formatter
/// library via the _formatter_parser / _formatter_field_name_split
/// methods.
///
/// We parse this format:
///
/// replacement_field = "{" field_name ["!" conversion] [":" format_spec] "}"
/// field_name = (identifier | integer) ("." attribute_name | "[" element_index "]")*
/// attribute_name = identifier
/// element_index = identifier
/// conversion = "r" | "s"
/// format_spec = any char, { must be balanced (for computed values), passed to __format__ method on object
/// </summary>
internal sealed class NewStringFormatter {
private static readonly char[]/*!*/ _brackets = new[] { '{', '}' };
private static readonly char[]/*!*/ _fieldNameEnd = new[] { '{', '}', '!', ':' };
#region Public APIs
/// <summary>
/// Runs the formatting operation on the given format and keyword arguments
/// </summary>
public static string/*!*/ FormatString(PythonContext/*!*/ context, string/*!*/ format, PythonTuple/*!*/ args, IDictionary<object, object>/*!*/ kwArgs) {
ContractUtils.RequiresNotNull(context, "context");
ContractUtils.RequiresNotNull(format, "format");
ContractUtils.RequiresNotNull(args, "args");
ContractUtils.RequiresNotNull(kwArgs, "kwArgs");
return Formatter.FormatString(context, format, args, kwArgs);
}
/// <summary>
/// Gets the formatting information for the given format. This is a list of tuples. The tuples
/// include:
///
/// text, field name, format spec, conversion
/// </summary>
public static IEnumerable<PythonTuple/*!*/>/*!*/ GetFormatInfo(string/*!*/ format) {
ContractUtils.RequiresNotNull(format, "format");
return StringFormatParser.Parse(format);
}
/// <summary>
/// Parses a field name returning the argument name and an iterable
/// object which can be used to access the individual attribute
/// or element accesses. The iterator yields tuples of:
///
/// bool (true if attribute, false if element index), attribute/index value
/// </summary>
public static PythonTuple/*!*/ GetFieldNameInfo(string/*!*/ name) {
ContractUtils.RequiresNotNull(name, "name");
FieldName fieldName = ParseFieldName(name, false);
if (String.IsNullOrEmpty(fieldName.ArgumentName)) {
throw PythonOps.ValueError("empty field name");
}
int val;
object argName = fieldName.ArgumentName;
if (Int32.TryParse(fieldName.ArgumentName, out val)) {
argName = ScriptingRuntimeHelpers.Int32ToObject(val);
}
return PythonTuple.MakeTuple(
argName,
AccessorsToPython(fieldName.Accessors)
);
}
#endregion
#region Parsing
/// <summary>
/// Base class used for parsing the format. Subclasss override Text/ReplacementField methods. Those
/// methods get called when they call Parse and then they can do the appropriate actions for the
/// format.
/// </summary>
private struct StringFormatParser {
private readonly string/*!*/ _str;
private int _index;
private StringFormatParser(string/*!*/ text) {
Assert.NotNull(text);
_str = text;
_index = 0;
}
/// <summary>
/// Gets an enumerable object for walking the parsed format.
///
/// TODO: object array? struct?
/// </summary>
public static IEnumerable<PythonTuple/*!*/>/*!*/ Parse(string/*!*/ text) {
return new StringFormatParser(text).Parse();
}
/// <summary>
/// Provides an enumerable of the parsed format. The elements of the tuple are:
/// the text preceding the format information
/// the field name
/// the format spec
/// the conversion
/// </summary>
private IEnumerable<PythonTuple/*!*/>/*!*/ Parse() {
int lastTextStart = 0;
while (_index != _str.Length) {
lastTextStart = _index;
_index = _str.IndexOfAny(_brackets, _index);
if (_index == -1) {
// no more formats, send the remaining text.
yield return PythonTuple.MakeTuple(
_str.Substring(lastTextStart, _str.Length - lastTextStart),
null,
null,
null);
break;
}
yield return ParseFormat(lastTextStart);
}
}
private PythonTuple/*!*/ ParseFormat(int lastTextStart) {
// check for {{ or }} and get the text string that we've skipped over
string text;
if (ParseDoubleBracket(lastTextStart, out text)) {
return PythonTuple.MakeTuple(text, null, null, null);
}
int bracketDepth = 1;
char? conversion = null;
string formatSpec = String.Empty;
// all entries have a field name, read it first
string fldName = ParseFieldName(ref bracketDepth);
// check for conversion
bool end = CheckEnd();
if (!end && _str[_index] == '!') {
conversion = ParseConversion();
}
// check for format spec
end = end || CheckEnd();
if (!end && _str[_index] == ':') {
formatSpec = ParseFormatSpec(ref bracketDepth);
}
// verify we hit the end of the format
end = end || CheckEnd();
if (!end) {
throw PythonOps.ValueError("expected ':' after format specifier");
}
// yield the replacement field information
return PythonTuple.MakeTuple(
text,
fldName,
formatSpec,
conversion.HasValue ?
conversion.ToString() :
null
);
}
/// <summary>
/// Handles {{ and }} within the string. Returns true if a double bracket
/// is found and yields the text
/// </summary>
private bool ParseDoubleBracket(int lastTextStart, out string/*!*/ text) {
if (_str[_index] == '}') {
// report the text w/ a single } at the end
_index++;
if (_index == _str.Length || _str[_index] != '}') {
throw PythonOps.ValueError("Single '}}' encountered in format string");
}
text = _str.Substring(lastTextStart, _index - lastTextStart);
_index++;
return true;
} else if (_index == _str.Length - 1) {
throw PythonOps.ValueError("Single '{{' encountered in format string");
} else if (_str[_index + 1] == '{') {
// report the text w/ a single { at the end
text = _str.Substring(lastTextStart, ++_index - lastTextStart);
_index++;
return true;
} else {
// yield the text
text = _str.Substring(lastTextStart, _index++ - lastTextStart);
return false;
}
}
/// <summary>
/// Parses the conversion character and returns it
/// </summary>
private char ParseConversion() {
_index++; // eat the !
if (CheckEnd()) {
throw PythonOps.ValueError("end of format while looking for conversion specifier");
}
return _str[_index++];
}
/// <summary>
/// Checks to see if we're at the end of the format. If there's no more characters left we report
/// the error, otherwise if we hit a } we return true to indicate parsing should stop.
/// </summary>
private bool CheckEnd() {
if (_index == _str.Length) {
throw PythonOps.ValueError("unmatched '{{' in format");
} else if (_str[_index] == '}') {
_index++;
return true;
}
return false;
}
/// <summary>
/// Parses the format spec string and returns it.
/// </summary>
private string/*!*/ ParseFormatSpec(ref int depth) {
_index++; // eat the :
return ParseFieldOrSpecWorker(_brackets, ref depth);
}
/// <summary>
/// Parses the field name and returns it.
/// </summary>
private string/*!*/ ParseFieldName(ref int depth) {
return ParseFieldOrSpecWorker(_fieldNameEnd, ref depth);
}
/// <summary>
/// Handles parsing the field name and the format spec and returns it. At the parse
/// level these are basically the same - field names just have more terminating characters.
///
/// The most complex part of parsing them is they both allow nested braces and require
/// the braces are matched. Strangely though the braces need to be matched across the
/// combined field and format spec - not within each format.
/// </summary>
private string/*!*/ ParseFieldOrSpecWorker(char[]/*!*/ ends, ref int depth) {
int end = _index - 1;
bool done = false;
do {
end = _str.IndexOfAny(ends, end + 1);
if (end == -1) {
throw PythonOps.ValueError("unmatched '{{' in format");
}
switch (_str[end]) {
case '{': depth++; break;
case '}': depth--; break;
default: done = true; break;
}
} while (!done && depth != 0);
string res = _str.Substring(_index, end - _index);
_index = end;
return res;
}
}
#endregion
#region String Formatter
/// <summary>
/// Provides the built-in string formatter which is exposed to Python via the str.format API.
/// </summary>
private class Formatter {
private readonly PythonContext/*!*/ _context;
private readonly PythonTuple/*!*/ _args;
private readonly IDictionary<object, object>/*!*/ _kwArgs;
private readonly int _depth;
private int _autoNumberedIndex;
private Formatter(PythonContext/*!*/ context, PythonTuple/*!*/ args, IDictionary<object, object>/*!*/ kwArgs, int depth)
: this(context, args, kwArgs) {
_depth = depth;
}
private Formatter(PythonContext/*!*/ context, PythonTuple/*!*/ args, IDictionary<object, object>/*!*/ kwArgs) {
Assert.NotNull(context, args, kwArgs);
_context = context;
_args = args;
_kwArgs = kwArgs;
}
public static string/*!*/ FormatString(PythonContext/*!*/ context, string/*!*/ format, PythonTuple/*!*/ args, IDictionary<object, object>/*!*/ kwArgs) {
Assert.NotNull(context, args, kwArgs, format);
return new Formatter(context, args, kwArgs).ReplaceText(format);
}
public static string/*!*/ FormatString(PythonContext/*!*/ context, string/*!*/ format, PythonTuple/*!*/ args, IDictionary<object, object>/*!*/ kwArgs, int depth) {
Assert.NotNull(context, args, kwArgs, format);
if (depth == 2) {
throw PythonOps.ValueError("Max string recursion exceeded");
}
return new Formatter(context, args, kwArgs, depth).ReplaceText(format);
}
private string ReplaceText(string format) {
StringBuilder builder = new StringBuilder();
foreach (PythonTuple pt in StringFormatParser.Parse(format)) {
string text = (string)pt[0];
string fieldName = (string)pt[1];
string formatSpec = (string)pt[2];
string conversionStr = (string)pt[3];
char? conversion = conversionStr != null && conversionStr.Length > 0 ? conversionStr[0] : (char?)null;
builder.Append(text);
if (fieldName != null) {
// get the argument value
object argValue = GetArgumentValue(ParseFieldName(fieldName, true));
// apply the conversion
argValue = ApplyConversion(conversion, argValue);
// handle computed format specifiers
formatSpec = ReplaceComputedFormats(formatSpec);
// append the string
builder.Append(Builtin.format(_context.SharedContext, argValue, formatSpec));
}
}
return builder.ToString();
}
/// <summary>
/// Inspects a format spec to see if it contains nested format specs which
/// we need to compute. If so runs another string formatter on the format
/// spec to compute those values.
/// </summary>
private string/*!*/ ReplaceComputedFormats(string/*!*/ formatSpec) {
int computeStart = formatSpec.IndexOf('{');
if (computeStart != -1) {
formatSpec = FormatString(
_context,
formatSpec,
_args,
_kwArgs,
_depth + 1
);
}
return formatSpec;
}
/// <summary>
/// Given the field name gets the object from our arguments running
/// any of the member/index accessors.
/// </summary>
private object GetArgumentValue(FieldName fieldName) {
return DoAccessors(fieldName, GetUnaccessedObject(fieldName));
}
/// <summary>
/// Applies the known built-in conversions to the object if a conversion is
/// specified.
/// </summary>
private object ApplyConversion(char? conversion, object argValue) {
switch (conversion) {
case 'r':
argValue = PythonOps.Repr(_context.SharedContext, argValue);
break;
case 's':
argValue = PythonOps.ToString(_context.SharedContext, argValue);
break;
case null:
// no conversion specified
break;
default:
throw PythonOps.ValueError("Unknown conversion specifier {0}", conversion.Value);
}
return argValue;
}
/// <summary>
/// Gets the initial object represented by the field name - e.g. the 0 or
/// keyword name.
/// </summary>
private object GetUnaccessedObject(FieldName fieldName) {
int argIndex;
object argValue;
// get the object
if (fieldName.ArgumentName.Length == 0) {
// auto-numbering of format specifiers
if (_autoNumberedIndex == -1) {
throw PythonOps.ValueError("cannot switch from manual field specification to automatic field numbering");
}
argValue = _args[_autoNumberedIndex++];
} else if (Int32.TryParse(fieldName.ArgumentName, out argIndex)) {
if (_autoNumberedIndex > 0) {
throw PythonOps.ValueError("cannot switch from automatic field numbering to manual field specification");
}
_autoNumberedIndex = -1;
argValue = _args[argIndex];
} else {
argValue = _kwArgs[fieldName.ArgumentName];
}
return argValue;
}
/// <summary>
/// Given the object value runs the accessors in the field name (if any) against the object.
/// </summary>
private object DoAccessors(FieldName fieldName, object argValue) {
foreach (FieldAccessor accessor in fieldName.Accessors) {
// then do any accesses against the object
int intVal;
if (accessor.IsField) {
argValue = PythonOps.GetBoundAttr(
_context.SharedContext,
argValue,
accessor.AttributeName
);
} else if (Int32.TryParse(accessor.AttributeName, out intVal)) {
argValue = PythonOps.GetIndex(
_context.SharedContext,
argValue,
ScriptingRuntimeHelpers.Int32ToObject(intVal)
);
} else {
argValue = PythonOps.GetIndex(
_context.SharedContext,
argValue,
accessor.AttributeName
);
}
}
return argValue;
}
}
#endregion
#region Parser helper functions
/// <summary>
/// Parses the field name including attribute access or element indexing.
/// </summary>
private static FieldName ParseFieldName(string/*!*/ str, bool reportErrors) {
// (identifier | integer) ("." attribute_name | "[" element_index "]")*
int index = 0;
string arg = ParseIdentifier(str, false, ref index);
return new FieldName(arg, ParseFieldAccessors(str, index, reportErrors));
}
/// <summary>
/// Parses the field name including attribute access or element indexing.
/// </summary>
private static IEnumerable<FieldAccessor> ParseFieldAccessors(string/*!*/ str, int index, bool reportErrors) {
// (identifier | integer) ("." attribute_name | "[" element_index "]")*
while (index != str.Length && str[index] != '}') {
char accessType = str[index];
if (accessType == '.' || accessType == '[') {
index++;
bool isIndex = accessType == '[';
string identifier = ParseIdentifier(str, isIndex, ref index);
if (isIndex) {
if (index == str.Length || str[index] != ']') {
throw PythonOps.ValueError("Missing ']' in format string");
}
index++;
}
if (identifier.Length == 0) {
throw PythonOps.ValueError("Empty attribute in format string");
}
yield return new FieldAccessor(identifier, !isIndex);
} else {
if (reportErrors) {
throw PythonOps.ValueError("Only '.' and '[' are valid in format field specifier, got {0}", accessType);
} else {
break;
}
}
}
}
/// <summary>
/// Converts accessors from our internal structure into a PythonTuple matching how CPython
/// exposes these
/// </summary>
private static IEnumerable<PythonTuple> AccessorsToPython(IEnumerable<FieldAccessor> accessors) {
foreach (FieldAccessor accessor in accessors) {
int val;
object attrName = accessor.AttributeName;
if (Int32.TryParse(accessor.AttributeName, out val)) {
attrName = ScriptingRuntimeHelpers.Int32ToObject(val);
}
yield return PythonTuple.MakeTuple(
ScriptingRuntimeHelpers.BooleanToObject(accessor.IsField),
attrName
);
}
}
/// <summary>
/// Parses an identifier and returns it
/// </summary>
private static string/*!*/ ParseIdentifier(string/*!*/ str, bool isIndex, ref int index) {
int start = index;
while (index < str.Length && str[index] != '.' && (isIndex || str[index] != '[') && (!isIndex || str[index] != ']')) {
index++;
}
return str.Substring(start, index - start);
}
/// <summary>
/// Encodes all the information about the field name.
/// </summary>
private struct FieldName {
public readonly string/*!*/ ArgumentName;
public readonly IEnumerable<FieldAccessor>/*!*/ Accessors;
public FieldName(string/*!*/ argumentName, IEnumerable<FieldAccessor>/*!*/ accessors) {
Assert.NotNull(argumentName, accessors);
ArgumentName = argumentName;
Accessors = accessors;
}
}
/// <summary>
/// Encodes a single field accessor (.b or [number] or [str])
/// </summary>
private struct FieldAccessor {
public readonly string AttributeName;
public readonly bool IsField;
public FieldAccessor(string attributeName, bool isField) {
AttributeName = attributeName;
IsField = isField;
}
}
#endregion
}
}