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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Read Data From A BLOB Incrementally</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(../images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(../images/sw.png) 0% 100% no-repeat }.ne { background: url(../images/ne.png) 100% 0% no-repeat }.nw { background: url(../images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="../index.html"><img class="logo" src="../images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="../about.html">About</a> <a href="../sitemap.html">Sitemap</a> <a href="../docs.html">Documentation</a> <a href="../download.html">Download</a> <a href="../copyright.html">License</a> <a href="../news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="../support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Read Data From A BLOB Incrementally</h2><blockquote><pre>int sqlite3_blob_read(sqlite3_blob *, void *Z, int N, int iOffset);</pre></blockquote><p>This function is used to read data from an open <a href="../c3ref/blob.html">BLOB handle</a> into acaller-supplied buffer. N bytes of data are copied into buffer Zfrom the open BLOB, starting at offset iOffset.</p><p>If offset iOffset is less than N bytes from the end of the BLOB,<a href="../c3ref/c_abort.html">SQLITE_ERROR</a> is returned and no data is read. If N or iOffset isless than zero, <a href="../c3ref/c_abort.html">SQLITE_ERROR</a> is returned and no data is read.</p><p>An attempt to read from an expired <a href="../c3ref/blob.html">BLOB handle</a> fails with anerror code of <a href="../c3ref/c_abort.html">SQLITE_ABORT</a>.</p><p>On success, SQLITE_OK is returned.Otherwise, an <a href="../c3ref/c_abort.html">error code</a> or an <a href="../c3ref/c_ioerr_access.html">extended error code</a> is returned.</p><p><h3>Invariants:</h3><table border="0" cellpadding="5" cellspacing="0"><tr><td valign="top">H17853</td> <td valign="top">A successful invocation of <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,Z,N,X)</a>shall reads N bytes of data out of the BLOB referenced by<a href="../c3ref/blob.html">BLOB handle</a> P beginning at offset X and store those bytesinto buffer Z.</td></tr><tr><td valign="top">H17856</td> <td valign="top">In <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,Z,N,X)</a> if the size of the BLOBis less than N+X bytes, then the function shall leave theZ buffer unchanged and return <a href="../c3ref/c_abort.html">SQLITE_ERROR</a>.</td></tr><tr><td valign="top">H17859</td> <td valign="top">In <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,Z,N,X)</a> if X or N is less than zerothen the function shall leave the Z buffer unchangedand return <a href="../c3ref/c_abort.html">SQLITE_ERROR</a>.</td></tr><tr><td valign="top">H17862</td> <td valign="top">The <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,Z,N,X)</a> interface shall return <a href="../c3ref/c_abort.html">SQLITE_OK</a>if N bytes are successfully read into buffer Z.</td></tr><tr><td valign="top">H17863</td> <td valign="top">If the <a href="../c3ref/blob.html">BLOB handle</a> P is expired and X and N are within boundsthen <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,Z,N,X)</a> shall leave the Z bufferunchanged and return <a href="../c3ref/c_abort.html">SQLITE_ABORT</a>.</td></tr><tr><td valign="top">H17865</td> <td valign="top">If the requested read could not be completed,the <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,Z,N,X)</a> interface shall return anappropriate <a href="../c3ref/c_abort.html">error code</a> or <a href="../c3ref/c_ioerr_access.html">extended error code</a>.</td></tr><tr><td valign="top">H17868</td> <td valign="top">If an error occurs during evaluation of <a href="../c3ref/blob_read.html">sqlite3_blob_read(P,...)</a>then subsequent calls to <a href="../c3ref/errcode.html">sqlite3_errcode(D)</a>,<a href="../c3ref/errcode.html">sqlite3_extended_errcode()</a>,<a href="../c3ref/errcode.html">sqlite3_errmsg(D)</a>, and <a href="../c3ref/errcode.html">sqlite3_errmsg16(D)</a> shall returninformation appropriate for that error, where D is the<a href="../c3ref/sqlite3.html">database connection</a> that was used to open the <a href="../c3ref/blob.html">BLOB handle</a> P.</td></tr></table></p><p>See also lists of <a href="objlist.html">Objects</a>, <a href="constlist.html">Constants</a>, and <a href="funclist.html">Functions</a>.</p><hr><small><i>This page last modified 2008/12/09 18:44:04 UTC</i></small></div></body></html>⌨️ 快捷键说明
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