.Dd December 19, 2018
.Dt SQLITE3CHANGESET_INVERT 3
.Os
.Sh NAME
.Nm sqlite3changeset_invert
.Nd Invert A Changeset
.Sh SYNOPSIS
.Ft int 
.Fo sqlite3changeset_invert
.Fa "int nIn"
.Fa "const void *pIn"
.Fa "int *pnOut"
.Fa "void **ppOut        "
.Fc
.Sh DESCRIPTION
This function is used to "invert" a changeset object.
Applying an inverted changeset to a database reverses the effects of
applying the uninverted changeset.
Specifically: 
.Bl -bullet
.It
Each DELETE change is changed to an INSERT, and 
.It
Each INSERT change is changed to a DELETE, and 
.It
For each UPDATE change, the old.* and new.* values are exchanged.
.El
.Pp
This function does not change the order in which changes appear within
the changeset.
It merely reverses the sense of each individual change.
.Pp
If successful, a pointer to a buffer containing the inverted changeset
is stored in *ppOut, the size of the same buffer is stored in *pnOut,
and SQLITE_OK is returned.
If an error occurs, both *pnOut and *ppOut are zeroed and an SQLite
error code returned.
.Pp
It is the responsibility of the caller to eventually call sqlite3_free()
on the *ppOut pointer to free the buffer allocation following a successful
call to this function.
.Pp
WARNING/TODO: This function currently assumes that the input is a valid
changeset.
If it is not, the results are undefined.