/**
* read a < hex string >. The initial < has already been read.
*
* @param objNum the object number of the object containing the dictionary being read; negative
* only if the object number is unavailable, which should only happen if we're reading a
* string placed directly in the trailer
* @param objGen the object generation of the object containing the object being read; negative
* only if the objNum is unavailable
* @param decrypter the decrypter to use
*/
private PDFObject readHexString(int objNum, int objGen, PDFDecrypter decrypter)
throws IOException {
// we've already read the <. Now get the hex bytes until >
int val;
StringBuffer sb = new StringBuffer();
while ((val = readHexPair()) >= 0) {
sb.append((char) val);
}
if (this.buf.get() != '>') {
throw new PDFParseException("Bad character in Hex String");
}
return new PDFObject(
this, PDFObject.STRING, decrypter.decryptString(objNum, objGen, sb.toString()));
}
/**
* read a ( character string ). The initial ( has already been read. Read until a *balanced* )
* appears.
*
* <p>Section 3.2.3 of PDF Refernce version 1.7 defines the format of String objects. Regarding
* literal strings:
*
* <blockquote>
*
* Within a literal string, the backslash (\) is used as an escape character for various purposes,
* such as to include newline characters, nonprinting ASCII characters, unbalanced parentheses, or
* the backslash character itself in the string. The character immediately following the backslash
* determines its precise interpretation (see Table 3.2). If the character following the backslash
* is not one of those shown in the table, the backslash is ignored.
*
* </blockquote>
*
* *
*
* <p>This only reads 8 bit basic character 'strings' so as to avoid a text string interpretation
* when one is not desired (e.g., for byte strings, as used by the decryption mechanism). For an
* interpretation of a string returned from this method, where the object type is defined as a
* 'text string' as per Section 3.8.1, Table 3.31 "PDF Data Types", {@link
* PDFStringUtil#asTextString} ()} or {@link PDFObject#getTextStringValue()} must be employed.
*
* @param objNum the object number of the object containing the dictionary being read; negative
* only if the object number is unavailable, which should only happen if we're reading a
* dictionary placed directly in the trailer
* @param objGen the object generation of the object containing the object being read; negative
* only if the objNum is unavailable
* @param decrypter the decrypter to use
*/
private PDFObject readLiteralString(int objNum, int objGen, PDFDecrypter decrypter)
throws IOException {
int c;
// we've already read the (. now get the characters until a
// *balanced* ) appears. Translate \r \n \t \b \f \( \) \\ \ddd
// if a cr/lf follows a backslash, ignore the cr/lf
int parencount = 1;
StringBuffer sb = new StringBuffer();
while (parencount > 0) {
c = this.buf.get() & 0xFF;
// process unescaped parenthesis
if (c == '(') {
parencount++;
} else if (c == ')') {
parencount--;
if (parencount == 0) {
c = -1;
break;
}
} else if (c == '\\') {
// From the spec:
// Within a literal string, the backslash (\) is used as an
// escape character for various purposes, such as to include
// newline characters, nonprinting ASCII characters,
// unbalanced parentheses, or the backslash character itself
// in the string. The character immediately following the
// backslash determines its precise interpretation (see
// Table 3.2). If the character following the backslash is not
// one of those shown in the table, the backslash is ignored.
//
// summary of rules:
//
// \n \r \t \b \f 2-char sequences are used to represent their
// 1-char counterparts
//
// \( and \) are used to escape parenthesis
//
// \\ for a literal backslash
//
// \ddd (1-3 octal digits) for a character code
//
// \<EOL> is used to put formatting newlines into the
// file, but aren't actually part of the string; EOL may be
// CR, LF or CRLF
//
// any other sequence should see the backslash ignored
// grab the next character to see what we're dealing with
c = this.buf.get() & 0xFF;
if (c >= '0' && c < '8') {
// \ddd form - one to three OCTAL digits
int count = 0;
int val = 0;
while (c >= '0' && c < '8' && count < 3) {
val = val * 8 + c - '0';
c = this.buf.get() & 0xFF;
count++;
}
// we'll have read one character too many
this.buf.position(this.buf.position() - 1);
c = val;
} else if (c == 'n') {
c = '\n';
} else if (c == 'r') {
c = '\r';
} else if (c == 't') {
c = '\t';
} else if (c == 'b') {
c = '\b';
} else if (c == 'f') {
c = '\f';
} else if (c == '\r') {
// escaped CR to be ignored; look for a following LF
c = this.buf.get() & 0xFF;
if (c != '\n') {
// not an LF, we'll consume this character on
// the next iteration
this.buf.position(this.buf.position() - 1);
}
c = -1;
} else if (c == '\n') {
// escaped LF to be ignored
c = -1;
}
// any other c should be used as is, as it's either
// one of ()\ in which case it should be used literally,
// or the backslash should just be ignored
}
if (c >= 0) {
sb.append((char) c);
}
}
return new PDFObject(
this, PDFObject.STRING, decrypter.decryptString(objNum, objGen, sb.toString()));
}
