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.TH scan_utf8 3
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.SH NAME
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scan_utf8 \- decode an unsigned integer from UTF-8 encoding
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.SH SYNTAX
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.B #include <scan.h>
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size_t \fBscan_utf8\fP(const char *\fIsrc\fR,size_t \fIlen\fR,uint32_t *\fIdest\fR);
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size_t \fBscan_utf8_sem\fP(const char *\fIsrc\fR,size_t \fIlen\fR,uint32_t *\fIdest\fR);
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.SH DESCRIPTION
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scan_utf8 decodes an unsigned integer in UTF-8 encoding from a memory
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area holding binary data. It writes the decode value in \fIdest\fR and
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returns the number of bytes it read from \fIsrc\fR.
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scan_utf8 never reads more than \fIlen\fR bytes from \fIsrc\fR. If the
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sequence is longer than that, or the memory area contains an invalid
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sequence, scan_utf8 returns 0 and does not touch \fIdest\fR.
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The length of the longest valid UTF-8 sequence is 6.
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scan_utf8 will reject syntactically invalid encodings, but not
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semantically invalid ones. scan_utf8_sem will additionally reject
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surrogates.
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.SH NOTE
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fmt_utf8 and scan_utf8 implement the encoding from UTF-8, but are meant
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to be able to store integers, not just Unicode code points. Values
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above 0x10ffff are not valid UTF-8. If you are using this function to
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parse UTF-8, you need to reject them (see RFC 3629).
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.SH "SEE ALSO"
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fmt_utf8(3), scan_utf8_sem(3)
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