Ah.. ok. That makes sense. Grow() just ensures that some number of bytes can be written, and they could be, so it didn't do anything.
Thanks for the explanation. On Wednesday, December 20, 2017 at 3:01:29 AM UTC-5, Uli Kunitz wrote: > > Grow ensures that there are at least n bytes to write.The call to > bb.Grow(2) in the example will not change the underlying byte slice, > because there are already two bytes to write. A call to > bb.Grow(initial+growth), which is bb.Grow(4) in the example, will enlarge > the buffer to 8 bytes and will not result in a panic. > > The number of bytes available for writing are given by bb.Cap() - > bb.Len(). In the example bb.Len() stays 0 because nothing is written into > the buffer. I would also keep in mind that bb.Grow() is an optimization if > you are writing smaller data chunks into a buffer that gets larger than 64 > bytes to prevent multiple allocations and copies. Anyway your program > should work fine without calling Grow. > > Note also that bytes.Buffer works as an io.Reader and io.Writer. If you > don't need those interfaces a pure byte slice and the builtin append > function will be faster. > > Here is the changed program that doesn't panic: > https://play.golang.org/p/8nSATjpNjR > > On Wednesday, December 20, 2017 at 3:01:29 AM UTC-5, Uli Kunitz wrote: > > Grow ensures that there are at least n bytes to write.The call to > bb.Grow(2) in the example will not change the underlying byte slice, > because there are already two bytes to write. A call to > bb.Grow(initial+growth), which is bb.Grow(4) in the example, will enlarge > the buffer to 8 bytes and will not result in a panic. > > The number of bytes available for writing are given by bb.Cap() - > bb.Len(). In the example bb.Len() stays 0 because nothing is written into > the buffer. I would also keep in mind that bb.Grow() is an optimization if > you are writing smaller data chunks into a buffer that gets larger than 64 > bytes to prevent multiple allocations and copies. Anyway your program > should work fine without calling Grow. > > Note also that bytes.Buffer works as an io.Reader and io.Writer. If you > don't need those interfaces a pure byte slice and the builtin append > function will be faster. > > Here is the changed program that doesn't panic: > https://play.golang.org/p/8nSATjpNjR > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
