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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Diagnostics;
using System.Globalization;
using System.Xml.XPath;
namespace System.Xml
{
/// <summary>
/// Contains various static functions and methods for parsing and validating:
/// NCName (not namespace-aware, no colons allowed)
/// QName (prefix:local-name)
/// </summary>
internal static class ValidateNames
{
internal enum Flags
{
NCNames = 0x1, // Validate that each non-empty prefix and localName is a valid NCName
CheckLocalName = 0x2, // Validate the local-name
CheckPrefixMapping = 0x4, // Validate the prefix --> namespace mapping
All = 0x7,
AllExceptNCNames = 0x6,
AllExceptPrefixMapping = 0x3,
};
//-----------------------------------------------
// Nmtoken parsing
//-----------------------------------------------
/// <summary>
/// Attempts to parse the input string as an Nmtoken (see the XML spec production [7] && XML Namespaces spec).
/// Quits parsing when an invalid Nmtoken char is reached or the end of string is reached.
/// Returns the number of valid Nmtoken chars that were parsed.
/// </summary>
internal static int ParseNmtoken(string s, int offset)
{
Debug.Assert(s != null && offset <= s.Length);
// Keep parsing until the end of string or an invalid NCName character is reached
int i = offset;
while (i < s.Length)
{
if (XmlCharType.IsNCNameSingleChar(s[i]))
{
i++;
}
else
{
break;
}
}
return i - offset;
}
//-----------------------------------------------
// Nmtoken parsing (no XML namespaces support)
//-----------------------------------------------
/// <summary>
/// Attempts to parse the input string as an Nmtoken (see the XML spec production [7]) without taking
/// into account the XML Namespaces spec. What it means is that the ':' character is allowed at any
/// position and any number of times in the token.
/// Quits parsing when an invalid Nmtoken char is reached or the end of string is reached.
/// Returns the number of valid Nmtoken chars that were parsed.
/// </summary>
internal static int ParseNmtokenNoNamespaces(string s, int offset)
{
Debug.Assert(s != null && offset <= s.Length);
// Keep parsing until the end of string or an invalid Name character is reached
int i = offset;
while (i < s.Length)
{
if (XmlCharType.IsNameSingleChar(s[i]) || s[i] == ':')
{
i++;
}
else
{
break;
}
}
return i - offset;
}
// helper methods
internal static bool IsNmtokenNoNamespaces(string s)
{
int endPos = ParseNmtokenNoNamespaces(s, 0);
return endPos > 0 && endPos == s.Length;
}
//-----------------------------------------------
// Name parsing (no XML namespaces support)
//-----------------------------------------------
/// <summary>
/// Attempts to parse the input string as a Name without taking into account the XML Namespaces spec.
/// What it means is that the ':' character does not delimiter prefix and local name, but it is a regular
/// name character, which is allowed to appear at any position and any number of times in the name.
/// Quits parsing when an invalid Name char is reached or the end of string is reached.
/// Returns the number of valid Name chars that were parsed.
/// </summary>
internal static int ParseNameNoNamespaces(string s, int offset)
{
Debug.Assert(s != null && offset <= s.Length);
// Quit if the first character is not a valid NCName starting character
int i = offset;
if (i < s.Length)
{
if (XmlCharType.IsStartNCNameSingleChar(s[i]) || s[i] == ':')
{
i++;
}
else
{
return 0; // no valid StartNCName char
}
// Keep parsing until the end of string or an invalid NCName character is reached
while (i < s.Length)
{
if (XmlCharType.IsNCNameSingleChar(s[i]) || s[i] == ':')
{
i++;
}
else
{
break;
}
}
}
return i - offset;
}
// helper methods
internal static bool IsNameNoNamespaces(string s)
{
int endPos = ParseNameNoNamespaces(s, 0);
return endPos > 0 && endPos == s.Length;
}
//-----------------------------------------------
// NCName parsing
//-----------------------------------------------
/// <summary>
/// Attempts to parse the input string as an NCName (see the XML Namespace spec).
/// Quits parsing when an invalid NCName char is reached or the end of string is reached.
/// Returns the number of valid NCName chars that were parsed.
/// </summary>
internal static int ParseNCName(string s, int offset)
{
Debug.Assert(s != null && offset <= s.Length);
// Quit if the first character is not a valid NCName starting character
int i = offset;
if (i < s.Length)
{
if (XmlCharType.IsStartNCNameSingleChar(s[i]))
{
i++;
}
else
{
return 0; // no valid StartNCName char
}
// Keep parsing until the end of string or an invalid NCName character is reached
while (i < s.Length)
{
if (XmlCharType.IsNCNameSingleChar(s[i]))
{
i++;
}
else
{
break;
}
}
}
return i - offset;
}
internal static int ParseNCName(string s)
{
return ParseNCName(s, 0);
}
/// <summary>
/// Calls parseName and throws exception if the resulting name is not a valid NCName.
/// Returns the input string if there is no error.
/// </summary>
internal static string ParseNCNameThrow(string s)
{
// throwOnError = true
ParseNCNameInternal(s, true);
return s;
}
/// <summary>
/// Calls parseName and returns false or throws exception if the resulting name is not
/// a valid NCName. Returns the input string if there is no error.
/// </summary>
private static bool ParseNCNameInternal(string s, bool throwOnError)
{
int len = ParseNCName(s, 0);
if (len == 0 || len != s.Length)
{
// If the string is not a valid NCName, then throw or return false
if (throwOnError) ThrowInvalidName(s, 0, len);
return false;
}
return true;
}
//-----------------------------------------------
// QName parsing
//-----------------------------------------------
/// <summary>
/// Attempts to parse the input string as a QName (see the XML Namespace spec).
/// Quits parsing when an invalid QName char is reached or the end of string is reached.
/// Returns the number of valid QName chars that were parsed.
/// Sets colonOffset to the offset of a colon character if it exists, or 0 otherwise.
/// </summary>
internal static int ParseQName(string s, int offset, out int colonOffset)
{
int len, lenLocal;
// Assume no colon
colonOffset = 0;
// Parse NCName (may be prefix, may be local name)
len = ParseNCName(s, offset);
if (len != 0)
{
// Non-empty NCName, so look for colon if there are any characters left
offset += len;
if ((uint)offset < (uint)s.Length && s[offset] == ':')
{
// First NCName was prefix, so look for local name part
lenLocal = ParseNCName(s, offset + 1);
if (lenLocal != 0)
{
// Local name part found, so increase total QName length (add 1 for colon)
colonOffset = offset;
len += lenLocal + 1;
}
}
}
return len;
}
/// <summary>
/// Calls parseQName and throws exception if the resulting name is not a valid QName.
/// Returns the colon offset in the name.
/// </summary>
internal static int ParseQNameThrow(string s)
{
int colonOffset;
int len = ParseQName(s, 0, out colonOffset);
if (len == 0 || len != s.Length)
{
// If the string is not a valid QName, then throw
ThrowInvalidName(s, 0, len);
}
return colonOffset;
}
/// <summary>
/// Calls parseQName and throws exception if the resulting name is not a valid QName.
/// Returns the prefix and local name parts.
/// </summary>
internal static void ParseQNameThrow(string s, out string prefix, out string localName)
{
int colonOffset = ParseQNameThrow(s);
if (colonOffset != 0)
{
prefix = s.Substring(0, colonOffset);
localName = s.Substring(colonOffset + 1);
}
else
{
prefix = "";
localName = s;
}
}
/// <summary>
/// Parses the input string as a NameTest (see the XPath spec), returning the prefix and
/// local name parts. Throws an exception if the given string is not a valid NameTest.
/// If the NameTest contains a star, null values for localName (case NCName':*'), or for
/// both localName and prefix (case '*') are returned.
/// </summary>
internal static void ParseNameTestThrow(string s, out string? prefix, out string? localName)
{
int len, lenLocal, offset;
if (s.StartsWith('*'))
{
// '*' as a NameTest
prefix = localName = null;
len = 1;
}
else
{
// Parse NCName (may be prefix, may be local name)
len = ParseNCName(s, 0);
if (len != 0)
{
// Non-empty NCName, so look for colon if there are any characters left
localName = s.Substring(0, len);
if ((uint)len < (uint)s.Length && s[len] == ':')
{
// First NCName was prefix, so look for local name part
prefix = localName;
offset = len + 1;
if ((uint)offset < (uint)s.Length && s[offset] == '*')
{
// '*' as a local name part, add 2 to len for colon and star
localName = null;
len += 2;
}
else
{
lenLocal = ParseNCName(s, offset);
if (lenLocal != 0)
{
// Local name part found, so increase total NameTest length
localName = s.Substring(offset, lenLocal);
len += lenLocal + 1;
}
}
}
else
{
prefix = string.Empty;
}
}
else
{
// Make the compiler happy
prefix = localName = null;
}
}
if (len == 0 || len != s.Length)
{
// If the string is not a valid NameTest, then throw
ThrowInvalidName(s, 0, len);
}
}
/// <summary>
/// Throws an invalid name exception.
/// </summary>
/// <param name="s">String that was parsed.</param>
/// <param name="offsetStartChar">Offset in string where parsing began.</param>
/// <param name="offsetBadChar">Offset in string where parsing failed.</param>
internal static void ThrowInvalidName(string s, int offsetStartChar, int offsetBadChar)
{
// If the name is empty, throw an exception
if (offsetStartChar >= s.Length)
throw new XmlException(SR.Format(SR.Xml_EmptyName, string.Empty));
Debug.Assert(offsetBadChar < s.Length);
if (XmlCharType.IsNCNameSingleChar(s[offsetBadChar]) && !XmlCharType.IsStartNCNameSingleChar(s[offsetBadChar]))
{
// The error character is a valid name character, but is not a valid start name character
throw new XmlException(SR.Xml_BadStartNameChar, XmlException.BuildCharExceptionArgs(s, offsetBadChar));
}
else
{
// The error character is an invalid name character
throw new XmlException(SR.Xml_BadNameChar, XmlException.BuildCharExceptionArgs(s, offsetBadChar));
}
}
internal static Exception GetInvalidNameException(string s, int offsetStartChar, int offsetBadChar)
{
// If the name is empty, throw an exception
if (offsetStartChar >= s.Length)
return new XmlException(SR.Xml_EmptyName, string.Empty);
Debug.Assert(offsetBadChar < s.Length);
if (XmlCharType.IsNCNameSingleChar(s[offsetBadChar]) && !XmlCharType.IsStartNCNameSingleChar(s[offsetBadChar]))
{
// The error character is a valid name character, but is not a valid start name character
return new XmlException(SR.Xml_BadStartNameChar, XmlException.BuildCharExceptionArgs(s, offsetBadChar));
}
else
{
// The error character is an invalid name character
return new XmlException(SR.Xml_BadNameChar, XmlException.BuildCharExceptionArgs(s, offsetBadChar));
}
}
/// <summary>
/// Returns true if "prefix" starts with the characters 'x', 'm', 'l' (case-insensitive).
/// </summary>
internal static bool StartsWithXml(string s) =>
s.StartsWith("xml", StringComparison.OrdinalIgnoreCase);
/// <summary>
/// Returns true if "s" is a namespace that is reserved by Xml 1.0 or Namespace 1.0.
/// </summary>
internal static bool IsReservedNamespace(string s)
{
return s.Equals(XmlReservedNs.NsXml) || s.Equals(XmlReservedNs.NsXmlNs);
}
/// <summary>
/// Throw if the specified name parts are not valid according to the rules of "nodeKind". Check only rules that are
/// specified by the Flags.
/// NOTE: Namespaces should be passed using a prefix, ns pair. "localName" is always string.Empty.
/// </summary>
internal static void ValidateNameThrow(string? prefix, string localName, string? ns, XPathNodeType nodeKind, Flags flags)
{
// throwOnError = true
ValidateNameInternal(prefix, localName, ns, nodeKind, flags, true);
}
/// <summary>
/// Return false if the specified name parts are not valid according to the rules of "nodeKind". Check only rules that are
/// specified by the Flags.
/// NOTE: Namespaces should be passed using a prefix, ns pair. "localName" is always string.Empty.
/// </summary>
internal static bool ValidateName(string? prefix, string localName, string? ns, XPathNodeType nodeKind, Flags flags)
{
// throwOnError = false
return ValidateNameInternal(prefix, localName, ns, nodeKind, flags, false);
}
/// <summary>
/// Return false or throw if the specified name parts are not valid according to the rules of "nodeKind". Check only rules
/// that are specified by the Flags.
/// NOTE: Namespaces should be passed using a prefix, ns pair. "localName" is always string.Empty.
/// </summary>
private static bool ValidateNameInternal(string? prefix, string localName, string? ns, XPathNodeType nodeKind, Flags flags, bool throwOnError)
{
Debug.Assert(prefix != null && localName != null && ns != null);
if ((flags & Flags.NCNames) != 0)
{
// 1. Verify that each non-empty prefix and localName is a valid NCName
if (prefix.Length != 0)
if (!ParseNCNameInternal(prefix, throwOnError))
{
return false;
}
if (localName.Length != 0)
if (!ParseNCNameInternal(localName, throwOnError))
{
return false;
}
}
if ((flags & Flags.CheckLocalName) != 0)
{
// 2. Determine whether the local name is valid
switch (nodeKind)
{
case XPathNodeType.Element:
// Elements and attributes must have a non-empty local name
if (localName.Length == 0)
{
if (throwOnError) throw new XmlException(SR.Xdom_Empty_LocalName, string.Empty);
return false;
}
break;
case XPathNodeType.Attribute:
// Attribute local name cannot be "xmlns" if namespace is empty
if (ns.Length == 0 && localName.Equals("xmlns"))
{
if (throwOnError) throw new XmlException(SR.XmlBadName, new string[] { nodeKind.ToString(), localName });
return false;
}
goto case XPathNodeType.Element;
case XPathNodeType.ProcessingInstruction:
// PI's local-name must be non-empty and cannot be 'xml' (case-insensitive)
if (localName.Length == 0 || (localName.Length == 3 && StartsWithXml(localName)))
{
if (throwOnError) throw new XmlException(SR.Xml_InvalidPIName, localName);
return false;
}
break;
default:
// All other node types must have empty local-name
if (localName.Length != 0)
{
if (throwOnError) throw new XmlException(SR.XmlNoNameAllowed, nodeKind.ToString());
return false;
}
break;
}
}
if ((flags & Flags.CheckPrefixMapping) != 0)
{
// 3. Determine whether the prefix is valid
switch (nodeKind)
{
case XPathNodeType.Element:
case XPathNodeType.Attribute:
case XPathNodeType.Namespace:
if (ns.Length == 0)
{
// If namespace is empty, then prefix must be empty
if (prefix.Length != 0)
{
if (throwOnError) throw new XmlException(SR.Xml_PrefixForEmptyNs, string.Empty);
return false;
}
}
else
{
// Don't allow empty attribute prefix since namespace is non-empty
if (prefix.Length == 0 && nodeKind == XPathNodeType.Attribute)
{
if (throwOnError) throw new XmlException(SR.XmlBadName, new string[] { nodeKind.ToString(), localName });
return false;
}
if (prefix.Equals("xml"))
{
// xml prefix must be mapped to the xml namespace
if (!ns.Equals(XmlReservedNs.NsXml))
{
if (throwOnError) throw new XmlException(SR.Xml_XmlPrefix, string.Empty);
return false;
}
}
else if (prefix.Equals("xmlns"))
{
// Prefix may never be 'xmlns'
if (throwOnError) throw new XmlException(SR.Xml_XmlnsPrefix, string.Empty);
return false;
}
else if (IsReservedNamespace(ns))
{
// Don't allow non-reserved prefixes to map to xml or xmlns namespaces
if (throwOnError) throw new XmlException(SR.Xml_NamespaceDeclXmlXmlns, string.Empty);
return false;
}
}
break;
case XPathNodeType.ProcessingInstruction:
// PI's prefix and namespace must be empty
if (prefix.Length != 0 || ns.Length != 0)
{
if (throwOnError) throw new XmlException(SR.Xml_InvalidPIName, CreateName(prefix, localName));
return false;
}
break;
default:
// All other node types must have empty prefix and namespace
if (prefix.Length != 0 || ns.Length != 0)
{
if (throwOnError) throw new XmlException(SR.XmlNoNameAllowed, nodeKind.ToString());
return false;
}
break;
}
}
return true;
}
/// <summary>
/// Creates a colon-delimited qname from prefix and local name parts.
/// </summary>
private static string CreateName(string prefix, string localName)
{
return (prefix.Length != 0) ? $"{prefix}:{localName}" : localName;
}
/// <summary>
/// Split a QualifiedName into prefix and localname, w/o any checking.
/// (Used for XmlReader/XPathNavigator MoveTo(name) methods)
/// </summary>
internal static void SplitQName(string name, out string prefix, out string lname)
{
int colonPos = name.IndexOf(':');
if (-1 == colonPos)
{
prefix = string.Empty;
lname = name;
}
else if (0 == colonPos || (name.Length - 1) == colonPos)
{
throw new ArgumentException(SR.Format(SR.Xml_BadNameChar, XmlException.BuildCharExceptionArgs(':', '\0')), nameof(name));
}
else
{
prefix = name.Substring(0, colonPos);
colonPos++; // move after colon
lname = name.Substring(colonPos);
}
}
}
}
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