+
+ It is targetted to FreeType hackers, or more simply to developers who would like + a better understanding of the library's source code. +
+ +
+ But an example is certainly more meaningful than anything else:
+
+ can easily be replaced with:
+
+
+
+ Each FT_Get_Short or FT_Get_ULong call will read a big-endian integer + from the stream (2 bytes for FT_Get_Short, 4 bytes for FT_Get_ULong) + and advance the frame cursor accordingly. +
+ FT_Forget_Frame "releases" the frame from memory +
+ There are several advantages to using frames :
+
+
+ +
+ error must be a local variable of type FT_Error, + while stream must be a local variable or argument of type FT_Stream; +
+ The macro used to access a frame is ACCESS_Frame(_size_), it will + translate to:
+
+ Similarly, the macro FORGET_Frame() translates to:
+ Extracting integers can be performed with the GET_xxx macros, like:
+
+ (Note that an Offset is an integer stored with 3 bytes on the file).
+
+ All this means that the following code:
+
+ Can be replaced with macros by:
+
+ Which is clearer. Notice that error and stream must be defined
+ locally though for this code to work.. !!
+
+ FT_Forget_Frame(stream)
+
+
+
+
+
+ GET_Byte() FT_Get_Byte(stream)
+ GET_Char() ((FT_Char)FT_Get_Byte(stream))
+ GET_Short() FT_Get_Short(stream)
+ GET_UShort() ((FT_UShort)FT_Get_Short(stream))
+ GET_Offset() FT_Get_Offset(stream)
+ GET_UOffset() ((FT_ULong)FT_Get_Offset(stream))
+ GET_Long() FT_Get_Long(stream)
+ GET_ULong() ((FT_ULong)FT_Get_Long(stream))
+
+ error = FT_Access_Frame(stream, 2+4+4);
+
+ if (error) goto ...
+
+ str.value1 = FT_Get_Short(stream);
+ str.value2 = FT_Get_ULong(stream);
+ str.value3 = FT_Get_ULong(stream);
+
+ FT_Forget_Frame(stream);
+
+ if ( ACCESS_Frame( 2+4+4 ) ) goto ...
+
+
+ str.value1 = GET_Short();
+ str.value2 = GET_ULong();
+ str.value3 = GET_ULong();
+
+ FORGET_Frame();
+
+ +
+ For example, FT_Read_Short( stream, &error ) reads and returns a 2-byte + big-endian short from a stream, and place an error code in the error + variable. +
+ Thus, reading a single big-endian integer is shorter than using a frame for it. +
+ Note that there is also the macros READ_xxx() which translate to:
+
+ and can be used as in:
+
+ when error and stream are already defined locally.. +