Sometimes, you are not lucky enough to have perfect control over the encoding, number format and date format of the input, so you need to look ahead at a value sample to try and find out what those are.
Sometimes, you cannot even assume that the software that produced the file didn't mangle the quotes around fields, and you have to detect that you are 40960 bytes into a quoted field, decide that it's probably an error, and backtrack.
If you have enough memory to load the entire file, you will save a lot of time by giving up on streaming processing.
