std::basic_filebuf::seekoff
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<metanoindex/>
<tbody> </tbody> protected: virtual pos_type seekoff( off_type off, std::ios_base::seekdir way, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out ); |
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Positioniert den Dateizeiger, wenn möglich, in die Position, die genau
off Zeichen von Anfang, Ende, oder aktuelle Position der Datei (je nach dem Wert des way .Original:
Repositions the file pointer, if possible, to the position that corresponds to exactly
off characters from beginning, end, or current position of the file (depending on the value of way.The text has been machine-translated via Google Translate.
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Falls die zugehörige Datei nicht geöffnet ist (
is_open()==false, schlägt entspricht sofort .Original:
If the associated file is not open (
is_open()==false, fails immediately.The text has been machine-translated via Google Translate.
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Wenn die Multibyte-Zeichen-Kodierung ist state-abhängige (codecvt::encoding() kehrte
-1) oder variabler Länge (codecvt::encoding() kehrte 0) und der Offset off nicht 0, schlägt sofort:. kann diese Funktion nicht die Anzahl von Bytes, die zu entsprechen off Zeichen .Original:
If the multibyte character encoding is state-dependent (codecvt::encoding() returned
-1) or variable-length (codecvt::encoding() returned 0) and the offset off is not 0, fails immediately: this function cannot determine the number of bytes that correspond to off characters.The text has been machine-translated via Google Translate.
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Wenn
way nicht std::basic_ios::cur oder der Offset off nicht 0, und die meisten ärgern Betrieb auf dieser filebuf Objekt geschehen ausgegeben wurde (das heißt, entweder der Put-Puffer nicht leer ist, oder die zuletzt aufgerufene Funktion war overflow()), ruft dann die std::codecvt::unshift unshift Sequenz notwendig zu bestimmen, und schreibt diese Sequenz in die Datei durch Aufrufen overflow() .Original:
If
way is not std::basic_ios::cur or the offset off is not 0, and the most resent operation done on this filebuf object was output (that is, either the put buffer is not empty, or the most recently called function was overflow()), then calls std::codecvt::unshift to determine the unshift sequence necessary, and writes that sequence to the file by calling overflow().The text has been machine-translated via Google Translate.
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Dann wandelt das Argument
way auf einen Wert whence vom Typ int wie folgt:..Original:
Then converts the argument
way to a value whence of type int as follows:The text has been machine-translated via Google Translate.
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Wert
way Original: value of way The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
value of whence
|
std::basic_ios::beg
|
SEEK_SET |
std::basic_ios::end
|
SEEK_END |
std::basic_ios::cur
|
SEEK_CUR |
Dann, wenn das Zeichen Codierung mit fester Breite (
codecvt::encoding() gibt einige positive Zahl width, bewegt den Dateizeiger wie von std::fseek(file, width*off, whence) .Original:
Then, if the character encoding is fixed-width (
codecvt::encoding() returns some positive number width, moves the file pointer as if by std::fseek(file, width*off, whence).The text has been machine-translated via Google Translate.
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Ansonsten bewegt den Dateizeiger wie von
std::fseek(file, 0, whence) .Original:
Otherwise, moves the file pointer as if by
std::fseek(file, 0, whence).The text has been machine-translated via Google Translate.
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Die
openmode Argument, das die Funktion der Basisklasse Unterschrift erforderlich , ist in der Regel ignoriert, da std::basic_filebuf nur eine Datei Position hält .Original:
The
openmode argument, required by the base class function signature, is usually ignored, because std::basic_filebuf maintains only one file position.The text has been machine-translated via Google Translate.
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Parameter
| off | - | relativen Position, um die Position Indikator gesetzt .
Original: relative position to set the position indicator to. The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. | ||||||||||||||||||||||||||||||||
| dir | - | definiert Grundposition den relativen Offset zu bewerben. Es kann eine der folgenden Konstanten sein:
Original: defines base position to apply the relative offset to. It can be one of the following constants:
The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. | ||||||||||||||||||||||||||||||||
| which | - | Legt fest, welche der Ein-und / oder Ausgabe-Sequenzen zu beeinflussen. Es kann eine oder eine Kombination der folgenden Konstanten:
Original: defines which of the input and/or output sequences to affect. It can be one or a combination of the following constants:
The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. | ||||||||||||||||||||||||||||||||
Rückgabewert
ist ein neu konstruiertes Objekt vom Typ
pos_type die resultierende Datei Position oder pos_type(off_type(-1)) bei Ausfall speichert .Original:
A newly constructed object of type
pos_type which stores the resulting file position, or pos_type(off_type(-1)) on failure.The text has been machine-translated via Google Translate.
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Notes
seekoff() wird durch std::basic_streambuf::pubseekoff, die durch std::basic_istream::seekg genannt wird aufgerufen, std::basic_ostream::seekp, std::basic_istream::tellg und std::basic_ostream::tellpOriginal:
seekoff() is called by std::basic_streambuf::pubseekoff, which is called by std::basic_istream::seekg, std::basic_ostream::seekp, std::basic_istream::tellg, and std::basic_ostream::tellpThe text has been machine-translated via Google Translate.
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Beispiel
#include <iostream>
#include <fstream>
#include <locale>
int main()
{
// prepare a 10-byte file holding 4 characters in UTF8
std::ofstream("text.txt") << u8"z\u00df\u6c34\U0001d10b"; // or u8"zß水𝄋"
// or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";
// open using a non-converting encoding
std::ifstream f1("text.txt");
std::cout << "f1's locale's encoding() returns "
<< std::use_facet<std::codecvt<char, char, std::mbstate_t>>(f1.getloc()).encoding() << '\n'
<< "pubseekoff(3, beg) returns " << f1.rdbuf()->pubseekoff(3, std::ios_base::beg) << '\n'
<< "pubseekoff(0, end) returns " << f1.rdbuf()->pubseekoff(0, std::ios_base::end) << '\n';;
// open using UTF-8
std::wifstream f2("text.txt");
f2.imbue(std::locale("en_US.UTF-8"));
std::cout << "f2's locale's encoding() returns "
<< std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(f2.getloc()).encoding() << '\n'
<< "pubseekoff(3, beg) returns " << f2.rdbuf()->pubseekoff(3, std::ios_base::beg) << '\n'
<< "pubseekoff(0, end) returns " << f2.rdbuf()->pubseekoff(0, std::ios_base::end) << '\n';
}
Output:
f1's locale's encoding() returns 1
pubseekoff(3, beg) returns 3
pubseekoff(0, end) returns 10
f2's locale's encoding() returns 0
pubseekoff(3, beg) returns -1
pubseekoff(0, end) returns 10
Siehe auch
Beruft seekoff()Original: invokes seekoff()The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (öffentliche Elementfunktion of std::basic_streambuf)
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[virtuell] |
positioniert die Datei Position mit absoluter Adressierung Original: repositions the file position, using absolute addressing The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (virtuellen geschützten Member-Funktion) |
verschiebt die Datei Positionsanzeiger zu einer bestimmten Position in einer Datei Original: moves the file position indicator to a specific location in a file The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) | |